EMC CLARiiON Backup Storage Solutions

Transcription

1 Engineering White Paper Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup Abstract This white paper describes how to configure the CLARiiON CX600, CX400, and CX200 storage systems with CA BrightStor Enterprise Backup for best performance as destinations for backups. It also compares the benefits and performance characteristics of backup-to-disk versus backup-to-tape implementations. Published 4/16/2003

2 4/16/2003 Copyright 2003 EMC Corporation and Computer Associates. All rights reserved. EMC and Computer Associates believe the information in this publication is accurate as of its publication date. The information is subject to change without notice. THE INFORMATION IN THIS PUBLICATION IS PROVIDED AS IS. EMC CORPORATION AND COMPUTER ASSOCIATES MAKE NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WITH RESPECT TO THE INFORMATION IN THIS PUBLICATION, AND SPECIFICALLY DISCLAIM IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Use, copying, and distribution of any EMC or Computer Associates software described in this publication requires an applicable software license. All other trademarks used herein are the property of their respective owners. Part Number H882.2 Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 2

3 Table of Contents Summary...4 Introduction...4 Disk Backup Overview...4 Advantages of Backup-to-Disk... 5 Backup Performance... 5 Restore Performance... 5 Media Reliability and Data Availability... 6 Overall IT Efficiency... 6 CLARiiON Backup-to-Disk Performance Factors...6 RAID Types... 6 Factors Affecting I/O Sizes... 7 File System Block Size... 7 Disk-Array Element Size... 7 CLARiiON Configuration Settings... 7 Disk-Array Cache Settings... 7 LUNs per RAID Group... 8 Recommendations for Disk-Based Backups... 8 Windows File System Tuning... 8 Solaris File System Tuning... 8 EMC CLARiiON Storage Arrays...8 ATA Technology... 9 Computer Associates BrightStor Enterprise Backup...10 Device Configuration (Disk-Based) Device Configuration Window Backup Performance Analysis and Results...12 Dataset Description Aggregate Performance CLARiiON Raw Throughput Performance...13 Overall Backup/Restore Time CLARiiON Storage Array versus Native Tape Drive Performance BrightStor Enterprise Backup Performance Results...18 Backup and Restore Performance Results Conclusions...20 Appendix A: Tape Drive Characteristics...21 Appendix B: Related White Papers...22 Appendix C: Related Articles...23 Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 3

4 Summary Storage backup solutions that incorporate backup-to-disk yield significant benefits over traditional backupto-tape. These benefits include: Near-term recovery of mission-critical data Rapid restore from disk Greater reliability of the backup medium Multiple host data streams to disk As a complement to using tape for long-term storage, backup-to-disk is an emerging and powerful solution for rapid recovery of mission-critical data. There are many applications that require frequent retrievals of recently captured data, as well as the pervasive need for backup of crucial business data that must be preserved and retrieved quickly and efficiently. Leading-edge customers are using disk as the destination for storage management application output. Advanced Technology-Attached (ATA) disk technology provides benefits over tape with the performance of disk. Backup arrays or disk-based backups will not replace tape, but will shift tape into an archival role. Today, EMC recommends adopting a backup-to-disk solution when performance and data reliability are the customer s primary concern. Introduction This white paper describes implementing backup-to-disk technology with Computer Associates BrightStor Enterprise Backup and the many advantages over traditional backup-to-tape. This implementation has been tested and endorsed by both EMC and Computer Associates BrightStor engineering. This document contains information relating to BrightStor Enterprise Backup, and identifies what to expect from EMC CLARiiON storage systems when used as destinations of backups. It also compares the performance of CLARiiON storage systems to today s high-performance tape drives such as SDLT and LTO technologies. EMC s CLARiiON Application Solutions Integration and Performance Engineering teams performed tests using specific system configurations. Due to variations in hardware, software, disk layout, compressibility of data, system usage, and other factors, backup rates achieved in some situations may be different than those shown herein. All testing performed by the Applications Solutions Integration and Performance Engineering teams used the most up-to-date backup software available at that time. Other versions of these applications may yield other results. Disk Backup Overview Traditionally, backup software was created to write to a tape device. Today, most backup software products also support writing to disk, which means writing to a disk file in a file system. The file system may be on a Windows, NetWare, or UNIX platform, depending on the backup server. Disk-based RAID configurations enhance data protection beyond what tape can provide. With the CLARiiON CX series storage systems, backups to disk are equal to or faster than tape drives when comparing raw throughput performance. Backup and restore time using disk provides customers an advantage over using traditional tape. Disk drives are random access devices and can instantly start to transfer the files, whereas with tape, the tape must be loaded and then accessed, increasing the overall time. File system overhead and tape drives with on-board compression add more time lags. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 4

5 Under normal circumstances, I/O will always go to physical disk. Performances are generally characterized by the physical disk rotational speed and seek time together with the file system characteristics. Using a larger file system block size or allocation unit size (cluster size) may improve performance of disk backups by using larger contiguous address space for files because the operating system allocates fewer groups of contiguous sectors. CLARiiON disk cache improves overall performance. Results show that running with write cache enabled will provide significantly better performance than when cache is turned off. This is true because most backup applications perform their I/O in sizes such as 32 KB and 64 KB. The CLARiiON engineering team examined the effects of various CLARiiON settings on physical write and read rates prior to running the tests, so that these settings could be varied during the backup tests. Benefits of CLARiiON disk-based backups that are discussed in more detail in this white paper include: Random access characteristics of disk versus sequential access for tape Simultaneous capability to read/write to disk Multiple host data streams Disk performance compared to tape performance with compression Aggregate performance Raw disk performance Advantages of Backup-to-Disk Traditionally, tape has been the backup medium of choice, due to its cost-per-mb advantages compared with disk. However, the economics of disk are narrowing that gap. The advantages of using disk over tape with backup solutions can be grouped into four major categories: Backup performance Restore performance Media reliability and data availability Overall IT efficiency The following sections summarize these benefits. Backup Performance CLARiiON storage systems are much faster than the new-technology tape drives such as SDLT and LTO. Some tape technologies respond to a minimal data stream by shoe-shining or excessive positioning. Disks do not experience this behavior because they are inherently random access. Restore Performance Faster recovery time for disk drives over tape and tape drives. The difference can be seconds or minutes, versus hours with tape. Disks support random and sequential access. Tapes support sequential access only. This enables faster access of data files, improving overall performance. If data is on several tape cartridges, the following steps are required to restore the data: 1. Each tape must be mounted by the library (up to a minute per tape). 2. The tape must load (30 seconds to a few minutes). 3. The tape must be positioned to the desired data (an average access time is a few minutes). Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 5

6 4. The tape must be rewound and unloaded (30 seconds to a few minutes). 5. Load the next tape and repeat cycle. Time to first byte takes milliseconds for disk versus seconds to minutes for tape. Media Reliability and Data Availability Media-specific errors, including faulty tape media, are reduced. Disk system RAID protection prevents data unavailability or data loss in the event of a disk drive failure. Tape handling is reduced or eliminated. Maintaining a set of tapes from a tape library can be problematic and requires properly trained personnel. Overall IT Efficiency Disk does not require the tape handling/positioning and RAID protection makes it inherently more reliable. There is less need to perform frequent full backups. Fewer backups need to be performed, saving network and CPU load. Tape undergoes a technology shift every three years, so a conversion process from old to new media must be undertaken at that interval. Disk technology does not go through these types of transitions since the format of the data is not changed as it is with tape technology. New larger-capacity disk drives reduce floor space requirements compared with equivalent-capacity tape libraries. CLARiiON Backup-to-Disk Performance Factors This section describes the specific parameters that can be altered to improve performance of backup-todisk. EMC varied these to determine recommended settings for best performance when backing up to a disk file. In addition to using backup software to measure CLARiiON performance, EMC also used lower-level tests to measure performance. Backup solutions that use disk as a backup destination, write sequentially to the disk. The source data (data that is read for backup) can be located anywhere on the source. Backup bandwidth to disk can be directly impacted by the fragmentation of the source or file system. Various backup packages write in particular block sizes. EMC tested sequential writes with block sizes of 32, 64, 128, and 256 KB. Note: EMC did not exhaustively test all the combinations of parameters. The number of permutations would be unrealistic to simulate. RAID Types CLARiiON storage systems use RAID technology to combine disks into one logical unit (LU) to improve reliability and/or performance. The CLARiiON storage system supports five RAID types; RAID 5, RAID 3, RAID 1, RAID 0, RAID 1/0. RAID 0 is a simple stripe and a single drive failure will result in loss of data. The other RAID types offer high availability and data reliability. The storage system can read and write to multiple disks simultaneously and independently and allow several read/write heads to work on the same task at once. EMC recommends RAID 5 RAID groups. They offer excellent read performance and good write performance. Write performance benefits greatly from CLARiiON storage-system caching. RAID 5 configurations are very suitable as disk-backup devices. RAID 1 devices are limited in terms of storage capacity; therefore, they do not lend themselves to backupto-disk solutions. RAID 1/0 devices offer both data availability and storage capacity but at a cost. This RAID configuration requires twice the number of disk drives, which increases the backup storage cost. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 6

7 RAID 3 devices are designed for bandwidth applications that are characterized as very large I/O, 1 MB in size and larger. Backup I/O sizes are typically smaller than this. A RAID 3 device cannot take advantage of the CLARiiON storage-system cache. RAID 5 configurations are very suitable as a disk-backup device. Destination backup devices are written to in a sequential pattern. The optimizations in FLARE for RAID 5 devices are a perfect fit for this type of application. The write requests are written to the write cache on the storage system and mirrored in the second storage processor write cache. FLARE then destages this data to disk in an MR3 manner. Factors Affecting I/O Sizes File System Block Size Operating systems allocate space for files in blocks. The file system block size varies depending on the OS being used. A larger file system block size provides a large I/O size, which can increase the bandwidth of a backup. Larger block sizes may reduce file system fragmentation. The fragmentation of a file system can also impact the backup bandwidth. The source file system (the file system being read for backup) should be as defragmented as possible. This helps the backup utility to perform read requests more sequentially. The default file system block size for UFS, the native Solaris file system, is 8 KB. UFS can be configured with either 4 KB or 8 KB. EMC recommends that the defaults be used. Disk-Array Element Size The element size of a RAID device is defined as some number of 512-byte sectors. The element size defines the RAID Group's stripe size, and this can have an impact on the behavior and therefore performance of a RAID device. The default element size for a RAID 5 device is 128, which is 64 KB. A five-drive RAID device has a stripe size of 256 KB. Algorithms in FLARE try to optimize back-end writes to a RAID 5 device. This type of optimized back-end I/O is termed MR3 writes. Note: EMC recommends using the default RAID 5 element size for devices that will be used for backup-to-disk devices. CLARiiON Configuration Settings This section describes the CLARiiON-specific parameters that can be altered to improve backup-to-disk performance. Disk-Array Cache Settings CLARiiON storage-system caching improves read and write performance for several types of RAID Groups. Read and write caching improve performance in two ways: For a read request, the array senses sequential reads from the host, and then starts to prefetch data from the back end into the read cache. The host then reads the data from cache. For a write request: SIncoming host write requests are written to cache and then mirrored to the second storage processor. The host request is then acknowledged. Writing the data to the cache allows for a faster response time. SIf the request modifies the same page in the write cache that has not yet been written to disk, the storage system updates the information in the cache before writing it to disk. One might anticipate that turning off the CLARiiON storage-system cache would benefit backups. However, EMC found a counter-intuitive result: Performance with the cache off was reduced, even when the writes were aligned on the proper boundaries (such as 256 KB). EMC found minor effects on Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 7

8 performance when varying the amount of memory dedicated to write cache. Similarly, little impact was noticed when varying the high and low watermarks. LUNs per RAID Group EMC recommends only using one LUN per RAID group for disk-based backup applications. Multiple LUNs are not recommended because concurrent I/O would cause the underlying physical disks to seek between the sectors used by the various LUNs, thereby deteriorating performance. Recommendations for Disk-Based Backups Consider the following disk-based backup guidelines when planning your CLARiiON configuration: Use a five-disk RAID 5 configuration. Use write cache. In some circumstances, having the write cache enabled will allow misaligned data to be written out as a hardware stripe (written as MR3). RAID 1/0 will give better performance than RAID 5 if boundaries are aligned. Windows File System Tuning Windows systems create a 63-sector hidden area on disk to house the Master Boot Record (MBR). This causes all I/O in the file system made on the subsequent partition to be misaligned (not on a 256 KB boundary), and therefore I/O performance will suffer. By using a program called diskpar, available on the Windows 2000 Resource Kit, you can alter the number of hidden blocks to a larger number so that the disk array I/Os are aligned and better optimized. Note: The disk defrag tool included in Windows 2000 will not work with cluster sizes greater than the default cluster size of 4 KB. Solaris File System Tuning There are two possible values to tune with Solaris. The first is to ensure that maxcontig for the file system in question is set high enough; otherwise, rotational delays will be incurred when laying down all the sectors in the write. Set maxcontig to the maximum number of sectors in a write. Since it may be difficult to know exactly what the backup software will use, EMC recommends setting maxcontig to 256 (equivalent to 128 KB since there are 512 bytes in a sector). The maxcontig value may be set when making a file system (such as with newfs) or later with tunefs. The second value that may be tuned is the maximum number of bytes that can be written in a single I/O. This value is by default 128 KB or 256 KB, depending on the hardware on which Solaris is running. There is little reason to go to 256 KB, because the backup software would have to change to take advantage of the larger I/O size. For completeness, this line may be added to allow 1 MB I/O: set maxphys= EMC CLARiiON Storage Arrays CLARiiON storage systems provide leading performance and investment protection. These storage solutions feature modular building blocks, based on advanced sixth-generation Fibre Channel technology. EMC Fibre Channel CX series disk-array storage systems provide terabytes of disk storage capacity, high transfer rates, flexible configurations, and highly available data at affordable price points. Hardware RAID features are provided two storage processors (SPs). There are three members of the CLARiiON CX-series storage system family: CX600, CX400, and CX200. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 8

9 4/16/2003 Figure 1. CLARiiON CX Series Overview ATA Technology EMC has implemented ATA disk technology with CLARiiON. This enables customers to keep more data online for longer periods of time. For many, previous alternatives were not affordable or justifiable. Customers can now mix and match performance Fibre Channel drives and capacity ATA drives within the same array, under common management. The CLARiiON software suite supports ATA drives. This singlearray implementation provides the deployment flexibility customers seek. To optimize CLARiiON storage systems for a backup-to-disk configuration, follow the guidelines in Table 1. Table 1. CLARiiON Disk-Based Configurations Guidelines CLARiiON Page Read Cache Write Watermark System Size SP-A SP-B Cache Low High CX KB 1,024 1,024 2, CX KB CX KB * Cache values are in MB Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 9

10 Computer Associates BrightStor Enterprise Backup BrightStor Enterprise Backup is designed to offer enterprise class backup/restore protection for centralized data center environments. Based on UNIX and Windows servers BrightStor Enterprise Backup is designed to deliver the highest performance, the highest levels of enterprise scalability and manageability and allow for very detailed customization to tightly integrate into your enterprise storage environment. BrightStor Enterprise Backup offers a wide range of enterprise class options and agents to offer the highest level of technology to protect every component of the enterprise. In the centralized data center, performance is a function of I/O throughput at the lowest possible levels of CPU and memory utilization, and this is exactly what BrightStor Enterprise Backup delivers to ensure unmatched performance. BrightStor Enterprise Backup is a backup software product used by many CLARiiON customers. The use of the SAN (storage area network) for backup of data on EMC CLARiiON storage systems allows valuable LAN (local area network) resources to be freed, increasing the backup and recovery performance. Additionally, tape libraries and tape drives can be shared among many hosts, each running different operating systems. EMC CLARiiON storage systems enhance the backup solution with their rich feature set. Backup and recovery solutions are more reliable and efficient by using features such as high availability, scalability, sharing capabilities, redundancy, and ease of upgrades. A wide variety of industry-standard components are used with BrightStor Enterprise Backup on EMC CLARiiON storage systems in a SAN. Each component is tested within a SAN environment to ensure its reliability and interoperability. This testing assures customers that their backup solution will work. Device Configuration (Disk-Based) CA BrightStor Enterprise Backup incorporates disk backup as file system devices. You must first configure file system devices in BrightStor Enterprise Backup s Device Configuration GUI in order to write to a disk file. Each file system device is a Windows folder that you specify. A device group may include a number of file system devices. Backup will migrate to another file system device when one is full. The following screen shows how to configure a CLARiiON file system device for backing up to disk: Figure 2. BrightStor Enterprise Backup Device Configuration Screen Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 10

11 Click File System Devices and click Next. The next screen is where you choose a destination for the folder on disk: Figure 3. BrightStor Enterprise Backup Destination Screen Device Configuration Window Once you have completed the setup procedure, you can go to BrightStor Enterprise Backup Device screen to view your configuration. For example, Figure 4 shows the information on the CX400 storage system. Figure 4. BrightStor Enterprise Backup Device Screen Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 11

12 Backup Performance Analysis and Results Customers who are considering moving to a backup-to-disk implementation are usually meeting their backup windows today. To be effective, backup-to-disk needs to be comparable to tape backup in all operational aspects including performance, overall completion time, and reliability. However, the adoption of backup-to-disk will not be driven by improvements in backup performance alone. The combination of affordable price points with the improved performance and reliability creates a compelling business proposition. A subset or single file restore from disk will provide a sizable improvement compared to restoring the file from tape. Disk-based implementations provide the random access characteristic of a disk drive when performing a restore task. With tape-based backups, you must also account for the library media load time, tape ready, seek time, etc. These can add several minutes to hours, in most cases, to the overall time it takes to complete, depending on the size of the restore operation. The following charts show the backup and restore results for the combinations of CLARiiON storage systems, tape drives, and configuration environments that were tested. In most cases, the Y-axis shows megabytes per second (MB/s) and the X-axis shows the file set used to back up and restore, unless otherwise noted. Dataset Description Large dataset (each directory is 2 GB) S1 GB size files 2 files S100 MB size files 20 files S10 MB size files 200 files S1 MB size files 2,000 files Small dataset (directory is 503 MB) S50 KB size files 10,000 files The performance charts show backup and restore from CLARiiON storage systems (CX600, CX400, and CX200), SDLT 320, SDLT 220, and LTO tape drives. You can use this information to compare tape drives with the CLARiiON storage system as a backup destination. Each CLARiiON storage system was configured with two RAID groups (RAID group 0 and RAID group 1), each on separate CLARiiON SPs (SP-A and SP-B) consisting of five drives each in a RAID 5 configuration. On the host systems, the two LUNs were called backup and restore. In a Microsoft Windows system, each one had its own drive letter. On Sun Solaris, there was a mount point for each one. Each of the dataset files had a representative 2:1 compression ratio. If there were no impediments reading the data from disk, and if the backup software was efficient writing to the destination device, throughputs to the tape devices would be double the native transfer rate. That implies backup rates of 22 MB/s to SDLT 220, 30 MB/s to LTO, and 32 MB/s to SDLT320 (since the native or uncompressed transfer rates are 11, 15, and 16 MB/s, respectively). Compressibility of data does not affect the rate at which backups can be done to disk; only tape drives have internal hardware compression. When data cannot be compressed, tape drives would be limited to their native transfer rates. Some file types that are already compressed include video and music files, pictures, zip files, and some database applications, to name just a few. In these scenarios, backup-to-disk performance compares even more favorably to tape than it does with compressible data. Aggregate Performance Total aggregate performance will vary depending on the type of CLARiiON storage system used, the type of backup host, file system and nature of the data. Expect a maximum per LUN throughput of 40 MB/s to 60 MB/s when only one or two LUNs are active. As more and more backup streams (LUNs) become active, the total aggregate throughput will increase. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 12

13 CLARiiON Raw Throughput Performance The CLARiiON storage arrays were tested for raw performance in read and copy operations. The purpose of the read test was to see how fast the data could be read from one LUN. The copy operation tested the CLARiiON for how fast it can read data from one LUN and write it to another LUN on separate RAID groups (and SPs). The following chart shows the results of these tests with the CX600, CX400, and CX200 storage arrays using both Fibre Channel disks (five disks) and serial-ata disks (nine disks). CLARiiON Raw Performance Throughput MB/Sec CX600 FC CX600 ATA CX400 FC CX400 ATA 20 CX200 FC 10 0 Read Copy Figure 5. CLARiiON Raw Performance Throughput Results Testing Environment CX200 CX400 CX600 Sun Solaris Enterprise 250 EMC DS-16B2 FC Switches Dell PE-2550 Windows 2000 CrossRoads 10K FC to SCSI Bridge SDLT 320 Tape drive SDLT 220 Tape drive HP LTO Dell PV-132T IBM LTO Internal FC Bridge Tape drive Figure 6. Backup-to-Disk SAN Testing Configuration Diagram Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 13

14 Overall Backup/Restore Time When comparing the performance of a backup-to-disk implementation to a backup-to-tape implementation, you must consider both the throughput performance and the overall time to complete a backup or restore. This section explains the vast difference in overall time it takes to perform a backup or restore task. In a backup scenario comparing backing up to disk versus backing up to tape, different steps are required to accomplish the job (2 GB in size). A brief description of each task is described along with the average time to complete. In a backup-to-disk scenario, the following steps are involved: Upon request, data starts to be transferred from the source (disk) to the destination (disk) (typically less than five seconds depending on backup application to start the transfer). Once the dataset has been backed up, the backup application can immediately start the next task. Disk-to-Disk Backup Time Total Elapsed Time :55 4% 96% File Access Time Xfer Data Figure 7. Overall Disk-to-Disk Backup Time The advantage of disk-based backups is the random access characteristic of disk drives along with their speed and (in the case of the CLARiiON storage arrays) data protections with RAID protection and redundancy protection. The overall time it took to back up a 2 GB dataset to disk was 55 seconds; the backup-to-tape took 3 minutes, 50 seconds. In a backup-to-tape scenario the following steps are involved: 1. Load a tape cartridge into a tape drive (10 seconds). 2. Wait for the drive to load the tape and become ready (15 seconds; up to 1 minute or more for a new tape media). 3. Tape drive must position the media to where the data will be written (up to 70 seconds or more). 4. Back up the data to tape (performance is determined by a variety of factors) 1. The data could need more than one tape media to complete the backup. Unload tape from drive (up to 70 seconds depending on position of tape). 1 Having a fast tape drive doesn't ensure the highest throughput. If the transfer rate of a tape drive is faster than the host data rate, the tape must stop and reposition frequently, degrading performance. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 14

15 5. Repeat the cycle for each tape that is required. Disk-to-Tape Backup Time Total Elapsed Time 3:50 4% 7% 31% 30% 28% Tape Load Tape Ready File Access Time Xfer Data Rewind/Unload Figure 8. Overall Disk-to-Tape Backup Time Only 28 percent of the overall time is actually transferring data to tape, the other 72 percent is tape mechanical movement, file access time, and other tasks. There is extensive overhead associated with backup-to-tape. Most applications will stop a backup job if a restore job is submitted. This means unloading the tape in the drive and loading the restore tape. When the restore job is finished, the backup job will continue. With disk-based configurations, both jobs can run simultaneously. This section explains the differences in overall time it takes to perform a restore of a typical dataset in a backup-to-disk scenario versus a tape restore. This example illustrates a typical scenario where a full backup was performed on one day followed by a daily incremental backup, and a subset of the data is to be restored. In a disk-to-disk restore scenario, the following steps are performed: 1. Upon request, data starts to be restored from the full backup set to the destination site (typically less than five seconds depending on backup application). 2. Once the full dataset has been restored, the first incremental dataset starts to restore, in most cases immediately. 3. The second incremental dataset starts once the first incremental dataset is completed. 4. Data is restored with no additional overhead time, as is the case with tape. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 15

16 Disk-to-Disk Restore Time Total Elapsed Time :45 4% 96% File Access Time Xfer Data Figure 9. Overall Disk-to-Disk Restore Time In the tape restore scenario, the following steps are needed to restore the data that may be scattered on several tapes: 1. Load the full backup tape into the drive (10 seconds). 2. Allow time for the drive to load the tape and become ready (15 seconds). 3. Wait for the tape drive to position the media to where the data resides (up to 70 seconds or more). 4. Restore the data to disk (performance is determined by a variety of factors) 2. The data could be on more than one tape, which will add to more overhead time. 5. Unload tape from drive (up to 70 seconds depending on position of tape). 6. Load the first incremental tape into a drive (up to 10 seconds). 7. Wait for the drive to load the tape and become ready (15 seconds). 8. Allow the tape drive to seek to where the data resides (up to 70 seconds or more). 9. Restore the data to disk. 10. Unload tape from drive (up to 70 seconds). 11. Load the second incremental tape into a drive (10 seconds). 12. Wait for the drive to load the tape and become ready (15 seconds). 13. Allow the tape drive to seek to where the data resides (up to 70 seconds or more). 14. Restore the data to disk. 2 Performance of any tape device with hardware compression depends on the compressibility of the data to achieve maximum performance of the tape drive; otherwise, performance will suffer. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 16

17 Data is restored. If files to be restored are not sequential on tape, you will need to add on more time for file seeks on the tape media. Tape-to-Disk Restore Time Total Elapsed Time 12:45 4% 6% 45% 37% 8% Tape Load Tape Ready File Access Time Xfer Data Rewind/Unload Figure 10. Overall Tape-to-Disk Restore Time These examples show a typical scenario where a subset of data is requested for restoration. As the chart shows, it took the disk-to-disk restore about 45 seconds to restore the data (1.5 GB). In the tape-to-disk scenario, it took roughly 12 minutes, 45 seconds to complete. This example also accounts for the fact that the requested data can be located on several incremental backup sets or media that all must be loaded and unloaded. Users should account for this overhead when comparing performance of restore media. Customers should consider their recovery time objective, reliability needs and footprint requirements when determining their optimal solution. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 17

18 CLARiiON Storage Array versus Native Tape Drive Performance The following chart shows performance results while backing up a dataset that is either already compressed or where the tape drives have compression turned off. CLARiiON vs. Tape Drive Performance CX600 FC CX600 ATA MB/Sec CX400 FC CX400 ATA CX200 FC SDLT 320 LTOs SDLT Figure 11. CLARiiON versus Native Tape Drive Performance with BrightStor Enterprise Backup The CLARiiON storage arrays perform two to four times faster than tape drives when the dataset is not compressible or tape drive hardware compression is turned off. Tape drives can compress data in hardware and achieve better performance. Backup software packages can compress through software. EMC found that performance suffered significantly when enabling this option, and EMC does not recommend using software compression unless customers are trying to conserve disk space. BrightStor Enterprise Backup Performance Results The following charts compare the performance of backing up to disk versus backing up to tape. The charts only show raw throughput of each device while data is being transferred and do not take into account tape positioning, file seek times, or library mechanical load/unload times. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 18

19 Backup and Restore Performance Results The following charts show the performance results using the large dataset with the CLARiiON storage systems in a disk-to-disk backup scenario with both FC disks and serial-ata disks versus a disk-to-tape scenario. BrightStor Enterprise Backup V10.5 Backup Performance Data 50 MB/Sec CX600 CX400 CX200 SDLT320 LTO SDLT220 0 Disk-to-Disk FC-to-FC Disk-to-Disk FC-to-ATA D-to-T FC-to-Tape Figure 12. Backup Performance Results BrightStor Enterprise Backup V10.5 Restore Performance Data 50 MB/Sec CX600 CX400 CX200 SDLT320 LTO SDLT220 0 Disk-to-Disk FC-to-FC Disk-to-Disk FC-to-ATA D-to-T FC-to-Tape Figure 13. Restore Performance Results Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 19

20 Conclusions Backup-to-disk is emerging as a technology that offers significant benefits over the traditional tape backup process. With the changing economics of disk technology, backup-to-disk solutions are now affordable. Leading-edge customers are implementing backup-to-disk solutions as improvements to their existing tape implementations. BrightStor Enterprise Backup offers the backup-to-disk functionality. It leverages the superior performance of CLARiiON storage systems. EMC engineering has tested and supports BrightStor Enterprise Backup with CLARiiON CX series arrays. Major advantages of backup-to-disk include: Backup performance Restore performance Media reliability and data availability Improve IT efficiency Elimination of tape positioning, tape errors, and other mechanical issues Improved backup reliability Backup array can be connected to a remote site for data mirrored (disk-to-disk) as a nondisruptive background IT task Raw Performance Results Table 2 shows the CX600 performance percentage gain over the tape drives tested with the large dataset using both FC disks and serial-ata disks as comparison. Table 2. CX600 Performance Gain over Tape Drives Tape Drive Backup Restore SDLT % 30% LTO 30% 35% SDLT % 51% CX400 and CX200 results, with the SDLT 320, LTO, and SDLT 220, are as follows: Backups are up to 13, 19, and 45 percent faster than the tape drives tested. Restores are up to 24, 29, and 46 percent greater. Also note the following: Disk-based backups can also benefit from using CLARiiON SnapView point-in-time snapshot capabilities for faster data recovery and efficient business processing. Tape will be used more for archival and offsite roles, instead of a front-end data collector. When configuring CLARiiON for backups, create an exclusive five-disk RAID 5 configuration with a single LUN per backup server. Multiple systems can share a CLARiiON storage system, with each system having exclusive use of one or more LUNs in the storage array for backup operations. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 20

21 Appendix A: Tape Drive Characteristics The following factors affect tape drive performance: Media positioning: When a backup or restore is performed, the storage device must position the tape so that the data is over the read/write head. Depending on the location of the data and the overall performance of the media device, this can take a significant amount of time. When you conduct performance analysis with media containing multiple images, it is important to account for the time lag that occurs before the data transfer starts. Tape streaming: If a tape device is being used at its most efficient speed, it is said to be streaming the data onto the tape. Generally speaking, if a tape device is streaming, there will be little physical stopping and starting of the media. Instead, the media will be constantly spinning within the tape drive. If the tape device is not being used at its most efficient speed, it may continually start and stop the media from spinning. This behavior is the opposite of tape streaming and usually results in a poor data throughput rate. Data compression: Most tape devices support some form of data compression within the tape device itself. Highly compressible data will yield a higher data throughput rate than uncompressible data if the tape device supports hardware data compression. This will be true even if the tape device is able to stream the data onto the tape for both the highly compressible data and the uncompressible data. Uncompressible data: If your data is already compressed or is not compressible, then the tape drives will be limited to their native transfer rates. Some file types that are already compressed include video and music files, pictures, zip files, and some database applications, to name just a few. Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 21

22 Appendix B: Related White Papers The following white papers are available on the EMC.com technical library: EMC CLARiiON CX-Series Backup-to-Disk Guide (with CX600, CX400, and CX200) EMC CLARiiON Backup-to-Disk Guide for the FC4700 EMC Designing a Backup Topology for Data on a CLARiiON Storage System : Computer Associates BrightStor ARCserve 2000 in SAN Environments Using the FC4700 and SnapView with Oracle8i EMC CLARiiON Database Storage Solutions: Oracle9i with SnapView in SAN Environments Using CLARiiON MirrorView with Oracle 8i in SAN Environments Storage Technology Choices for Microsoft SQL Server 2000 with CLARiiON Storage Systems EMC CLARiiON Database Storage Solutions: Best Practices for Microsoft SQL Server 2000 in SAN Environments EMC CLARiiON Application Storage Solutions: Disk Backup/Restore of Microsoft Exchange 2000 in SAN Environments EMC CLARiiON Application Storage Solutions: Installing Exchange 2000 with a Microsoft Cluster in SAN Environments EMC CLARiiON Database Storage Solutions: Microsoft SQL 2000 Cluster Installation in SAN Environments : Using EMC SnapView and MirrorView for Remote Backup in SAN Environments EMC CLARiiON Database Storage Solutions: Using EMC SnapView with Microsoft SQL Server in SAN Environments EMC Support Matrix (ESM) Can be found at: Configuring Your FC4x00 Storage System for Use with Backup Software Can be found by EMC customers at: Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 22

23 Appendix C: Related Articles The Enhanced Backup Solutions Initiative (EBSI) is a vendor-agnostic, industry coalition of storage companies dedicated to helping businesses better protect their mission-critical data with emerging hardware and software technologies for backup that maximize operational efficiency and cost savings. W. Curtis Preston s article, Surprise! Cheap Disks Cure Slow Backup, in Storage Magazine id35_gci828729,00.html Notes several downsides of tape and upsides of disk, and provides an example of how to apply disk. Preston also delivered the keynote speech, Rethinking Backup Design, at the February 2002 Easing Backup Pain conference sponsored by the Storage Networking Industry Association (SNIA). The article Beyond Backup: Ensuring Data Protection s&subsection=display&article_id= Contains the section Choosing the Right Backup/Recovery Approach, which is a nice quick comparison of disk-to-tape, disk-to-disk, point-in-time, and snapshot. The letter titled ATA Stacks Up from Quantum's co-founder argues convincingly against claims of ATA disk reliability problems. See it at: s&subsection=display&article_id= Scroll down for the second article on the page. Designing to Restore from Disk: Backup Futures 01.htm&page=1 Points out limitations in tape-based backup, and looks ahead to using disk-based point-in-time replication technologies. EMC is working with partners to leverage sophisticated storage array features for backups. A great article discussing this, Special Report: Shortening the Backup Window, appeared in the April 2002 issue of Storage Magazine: ci814808,00.html Backup-to-Disk Guide with Computer Associates BrightStor Enterprise Backup 23