VERITAS NetBackup & Data Domain DD200 Restorer

Transcription

1 PARTNER SOLUTIONS GUIDE VERITAS NetBackup & Data Domain DD200 Restorer HIGHLY RELIABLE, HIGH-PERFORMANCE DISK-BASED DATA PROTECTION AT THE COST OF TAPE VERSION INCLUDES TABLE OF CONTENTS STYLES 1

2 EXECUTIVE SUMMARY Continuous access to and protection of growing volumes of data is a fundamental business requirement. With falling disk prices, disk-based recovery is now viable for protecting data at an affordable price point, offering random access speeds to recover data. There is, however, a world of difference between simply writing backups to disk and designing specifically for disk-based data protection. VERITAS NetBackup has supported disk-based backups since the NetBackup 3.1 release, allowing simultaneous backups and restores on a disk storage unit. NetBackup 5.0 has greatly enhanced disk-based data protection with automatic disk staging, Synthetic Backup, and Inline Copy to leverage random access characteristics of disk. The Data Domain DD200 Restorer was designed to be an ideal disk storage unit for NetBackup. On the outside, it operates like a NAS system. On the inside, however, it is uniquely optimized for cost-efficient, fast, and reliable data protection. The DD200 Restorer provides 20x Global Compression to NetBackup backup and recovery data, delivering the capacity to retain months of backup images with the overall price-per-gb of tape automation. In addition, it offers unprecedented levels of data integrity, verification and self-healing, which are unavailable in traditional file systems or conventional disk systems. Together, NetBackup and the DD200 Restorer offer remarkable improvements in speed, reliability and TCO to any IT organization considering disk-based backup and recovery. This paper examines the benefits of the combined solution. It also evaluates backup, restore, and duplication performance using tape media and the Data Domain DD200 Restorer as a NetBackup disk storage unit. The combination of NetBackup and the Data Domain DD200 Restorer speeds up the recovery process by five fold, while increasing backup and tape duplication performance. Optimizing backup performance is no longer achieved at the expense of recovery performance. 2

3 Introduction... 4 Challenges with Backups to Disk...4 The Solution: VERITAS NetBackup and Data Domain DD200 Restorer...4 VERITAS Disk-Based Data Protection...4 Data Domain DD200 Restorer: An Overview...5 VERITAS and Data Domain Solution at Work... 5 Data Domain DD200 Restorer as VERITAS NetBackup Disk Storage Unit...6 Creating Offsite Tape Copies from Data Domain DD200 Restorer...6 Remote office backup with Data Domain replicator and Netbackup...6 High-Performance Recovery and Backup... 8 Increased Recovery Performance: 182% - 412% Faster than Tape...8 Partial Restore: 412% Faster than Tape...8 Full Restore: 182% Faster than Tape...9 Increased Backup Performance: 41% Faster than Tape...10 DD200-to-Tape Copying: 43% Faster than Tape-to-Tape Copying...11 On-site Recovery Capacity for Retaining Months of Backups Global Compression: Disk-Based Data Protection at the Cost of Tape...12 Benefits of Synthetic Backups on Data Domain DD200 Restorer...13 Highly Reliable, Proactive Verification of Data Recovery Data Domain Data Invulnerability Architecture...15 VERITAS NetBackup Media Verification Option...15 Simultaneous Access to Data Domain DD200 Restorer Simultaneous Backups, Restores, and Duplications...16 User-directed Restores without Impacting Regularly Scheduled Backups...16 Improved Disaster Recovery Capabilities for Offsite Archives Duplicating Backup Images...17 InLine Copy to Data Domain DD200 Restorer and Tape Simultaneously...17 Synthetic Backups from Data domain DD200 Restorer to Tape...17 One-step Recovery...17 Reduced Management Costs for On-Site Backup and Recovery Protection Seamless Integration into VERITAS NetBackup Environment...18 Elimination of Media Management for On-site Data Protection...18 Lower Tape Infrastructure Cost...18 Solution summary For more information contact...19 VERITAS contact Information...19 Data Domain Contact Information...19 Appendix: Test Environment Setup...20 Configuration...20 Data Set

4 INTRODUCTION CHALLENGES WITH BACKUPS TO DISK According to a 2004 survey by an independent storage industry analyst firm, Enterprise Storage Group, the biggest backup and recovery issues facing IT organizations are: Lengthy backup process Lengthy recovery process Inability to validate backup and recovery process Valuable staff hours required managing backup and recovery process Cumbersome media management With falling disk prices and availability of ATA-based disk arrays, disk has become a viable option for protecting data, and it can solve most of these problems. Recovery from disk is significantly faster than recovery from tape, and it can be completely automated. Most disk-based systems, however, are too expensive to serve as more than a small cache to tape. Disk arrays have a much higher capital cost than tape automation systems. Most enterprises need weeks or months of quick recoverability, which means many versions of files or databases must be saved on a daily basis. To save multiple versions on traditional disk storage becomes prohibitively expensive. In addition, storing them on a traditional file system has risks of its own; if the file system becomes inconsistent or corrupted, recovery data is lost. An effective disk-based backup and recovery solution requires enterprise-level backup and recovery software that takes advantage of disk as a random access device and a robust as well as a reliable storage system with enough capacity to store multiple backup images. This ensures high performance for both backup and recovery operations. Additionally, the storage capacity must be delivered at a cost comparable to tape. The solution must also ensure reliable and verifiable recoveries. THE SOLUTION: VERITAS NETBACKUP AND DATA DOMAIN DD200 RESTORER The combination of VERITAS NetBackup and the Data Domain DD200 Restorer provides a cost-effective, powerful disk-based data protection solution, focused on the integrity and reliability of data recovery. The combined solution delivers: Increased backup and recovery performance Concurrent backup, recovery, and duplication processes for more flexible data protection Highly reliable, proactive verification of data recoverability Disk-based data protection at the cost of tape automation, reducing the backup and recovery infrastructure TCO Onsite recovery capacity to retain months of backup images using a small footprint Improved disaster recovery capabilities for offsite archives Reduced management costs o Seamless integration with existing NetBackup environments o Elimination of media management issues for on-site backup and recovery protection VERITAS Disk-Based Data Protection VERITAS NetBackup has supported disk-based backup and recovery operations since NetBackup 3.1 with its disk storage unit for storing backup and archive data. NetBackup supports an unlimited number of disk storage units and allows up to 256 simultaneous operations to one disk storage unit, enabling concurrent backup, restore, 4

5 or duplication operations. NetBackup also manages the disk storage unit by automatically deleting expired backup images. NetBackup 5.0 or later significantly improves support for disk-based data protection with disk staging, Synthetic Backups, and Inline Copy. These features take advantage of random access capabilities of disk and portability benefits of tape to speed up backups and recoveries and to enhance offsite archiving and disaster recovery. Data Domain DD200 Restorer: An Overview The Data Domain DD200 Restorer is a specialized disk-based data recovery appliance with unprecedented levels of data compression, data protection, data integrity verification, and self-healing that are unavailable in conventional disk or tape systems. The DD200 Restorer seamlessly integrates with existing VERITAS NetBackup environments by presenting itself as an NFS or CIFS file server to a NetBackup master or media server as a disk storage unit. The DD200 Restorer is optimized for high throughput backup and recovery, continuous data verification, and high compression. This provides 23 TB of useable capacity to retain months of backup images at a cost competitive with tape-based storage and ensures highly reliable recoveries. VERITAS AND DATA DOMAIN SOLUTION AT WORK This section highlights configurations combining VERITAS NetBackup and the Data Domain DD200 Restorer: The Data Domain DD200 Restorer as a NetBackup disk storage unit Creating off-site tape copies from the Data Domain DD200 for disaster recovery or long-term archival purposes Remote office backup configurations using Data Domain Replicator to move data offsite Client A Client B Data Domain DD200 As a disk storage unit DD Replicator DD200 Replica In a DR site Client N... VERITAS NetBackup Master or Media Server Tape Library for offsite tape archive, as a destination for duplication 5

6 DATA DOMAIN DD200 RESTORER AS VERITAS NETBACKUP DISK STORAGE UNIT To the NetBackup media server, the Data Domain DD200 Restorer appears as a NFS/CIFS file server over Gigabit Ethernet. The DD200 Restorer can simply be added as a disk storage unit. Backup data is saved to the specified file path. Because it is a file server, no additional licenses are required, and no complex block storage provisioning is required. After the DD200 is mounted in a rack and cabled appropriately, configuration takes about 15 minutes, after which backups, restores, and duplicating to tape may begin. CREATING OFFSITE TAPE COPIES FROM DATA DOMAIN DD200 RESTORER NetBackup makes it very easy to duplicate images from one medium to another. A tape library and the DD200 Restorer are attached to the NetBackup master or media server. The DD200 Restorer serves as an onsite recovery repository and the tape library provides copies for off-site storage, a configuration that reduces the overall cost of the backup infrastructure and lowers operational costs and tape requirements. Daily backup and recovery windows no longer depend on the performance of the tape library. The duplication window is much larger than the original backup window, simplifying scheduling. The larger duplication window also reduces the number of tape drives required to complete the tape duplication process. NetBackup provides several ways to create tape copies for offsite archive: Duplication to tape InLine Copy to disk and tape simultaneously Synthetic Backups to tape The Disk Staging Storage Unit is not supported on the DD200 at this time. REMOTE OFFICE BACKUP WITH DATA DOMAIN REPLICATOR AND NETBACKUP All of the savings Data Domain Global Compression brings to storage also help WAN bandwidth costs in replication (see "Global Compression: Disk-based Data Protection at the Cost of Tape below for details). Using the Data Domain Replicator, two DD200s become asynchronous mirrors of each other. These replicating stores send only globally compressed deltas across the wire, so it is extremely cost effective for remote office configurations to have both the speed of local disk recovery and the safety of an online copy elsewhere. With NetBackup, it is very straightforward to backup to one and restore or duplicate to tape from either, with only nominal bandwidth overhead to get the data from point A to point B. No other system used as a disk store for NetBackup can offer anywhere near this level of efficiency on the WAN. Since WAN costs are high and not improving very fast, it is worth noting just how much better these factors might be. In comparing the size of data required for transmission across a network for remote backup on average for full backups, incremental backups, block-level incremental replication strategies and Data Domain Replicator, the differences are huge (the following are averages only, dependent on application mix): Full backup: Incremental backup: Block delta: DD Replicator w/nbu: n n / 20, or about 5% of a full n / 25, or about 4% of a full n / 125, or about 0.8% of a full 6

7 As shown in the diagram below, from the NetBackup perspective, the originating DD200 and the replica DD200 would be seen in the two sites by separate media managers as a single shared disk storage unit. This scenario is especially interesting for site failure recovery or recovery from a DD200 failure on one site. In a site failure, all files may be recovered on site B to a separate server infrastructure. The data will have remained online no matter what happens to Office A. To recover from a DD200 failure in site A, for file restores, Media Manager A could restore files by mounting the replica DD200 over the network. This would be slow for recovering all data to Office A, but would bridge a short term gap while provision is made for re-establishing the originating restorer. Office A Office B Backup Clients Backup Clients Backup Clients NBU Master Server IP NBU Media Manager A NBU Media Manager B Common Disk Storage Unit Mount Point Data Domain Replication A to B Duplicate to Tape Originator Replica To find out more about the Data Domain Replicator, see or contact your Data Domain representative. For complete flexibility in location of duplication and recovery, some minor scripting may be required to ensure that the correct media manager is used to get data from the correct DD200. 7

8 HIGH-PERFORMANCE RECOVERY AND BACKUP The combination of VERITAS NetBackup and the Data Domain DD200 Restorer delivers: Faster recoveries to meet ever-shrinking tolerance for downtime and to reduce rising costs of downtime Faster backups to meet ever-shrinking backup windows Faster and easier tape copies for off-site archive The DD200 Restorer s throughput is comparable with the current SDLT and LTO tape technology. In addition, Data Domain s real-time Global Compression technology, along with data integrity and consistency checks, does not compromise the appliance s performance. Unlike a tape drive, the DD200 Restorer does not require constant-speed streams of data for best performance. For additional performance and capacity, multiple DD200 Restorer units can simply be added to NetBackup configurations. Because it is a disk storage unit providing random access, file recoveries do not incur the seek time overhead of tape, so they go much faster. Because it is a file system interface, it supports sharing and simultaneous backups and restores, which can make the end-toend time of backup and duplication to tape faster. This section provides performance characteristics of the Data Domain DD200 Restorer and an LTO (Generation 2) tape drive for backup and recovery operations. The data set consists of an Oracle database and Exchange 2000 data, totaling 13.4 GB. See Appendix A for details of the test environment. It is important to note that the test environment was not designed to maximize performance; rather, it was set up to compare the two devices in a stable environment. INCREASED RECOVERY PERFORMANCE: 182% - 412% FASTER THAN TAPE By recovering data at the speed of disk, NetBackup can deliver an order of magnitude improvement in recovery performance and reduction in downtime costs. Recoveries from disk eliminate mounting, positioning, and unmounting delays associated with tape-based backups. Because of the DD200 Restorer s high useable capacity, it enables multiple months of data retention and allows recoveries to come from disk. Partial Restore: 412% Faster than Tape The random access advantage of disk is especially significant with a partial restore where only a few files need to be recovered. The partial or single file recovery performance is critical because according to an analyst firm, Strategic Research, 87% of all restores are single file recoveries, not full system recoveries. Our performance tests show that restoring a single file from the DD200 Restorer is 412% faster than restoring from an LTO-2 tape drive given the same environment and data sets. This restore test measured the elapsed time required to restore a randomly selected file of 4 GB in size. The DD200 Restorer s performance advantage can be greater if the data set is larger, the recovery requires a set of incremental backup images, or the tape backup is multiplexed. In these situations, the backup image would have spanned multiple tape cartridges and would have caused further tape-related delays of mounting, positioning, and unmounting. 8

9 Time to Restore a Single File Seconds DD200 Storage Units 319 LTO-2 Full Restore: 182% Faster than Tape In the performance tests, restoring an entire backup from the DD200 Restorer proved to be 182% faster than restoring from tape. The data transfer rate for the DD200 Restorer was 76 MB/s (or 268 GB/hr), compared to 27 MB/s (or 95 GB/hr) for the LTO-2 drive. In our tests, the backup was not multiplexed. The performance advantage of the DD200 Restorer would be even greater if multiplexing was used for the tape backup, if the recovery required processing multiple incremental backups, or if the backup spanned multiple tape cartridges. Time to Complete Full Restore Seconds DD200 Storage Units LTO-2 Increased recovery performance allows IT organizations to meet increasingly stringent service level agreements for time-to-recovery, resume business-critical applications more quickly, and reduce the impact of data loss. 9

10 INCREASED BACKUP PERFORMANCE: 41% FASTER THAN TAPE The combined solution of NetBackup and the DD200 Restorer optimizes backup performance while accelerating recovery performance. With increasing transfer rates of tape drives, backups need to be carefully tuned to stream a tape drive to avoid the shoe shine effect of starting, stopping, and repositioning the tape. As a result, multiplexing is used to maximize the tape drive utilization, compensating for slow clients, multiple slow networks, and short backups such as incremental backups. This helps backup performance but slows down restore performance significantly because it requires extra time to read backup images and skip data belonging to other backup clients. The combination of the disk storage unit and the DD200 Restorer allows multiple, simultaneous backup streams at varying speeds to be sent to one DD200 Restorer. Tuning the multiplexing for optimal performance is no longer required. The DD200 Restorer eliminates the negative effects of multiplexing. Our tests show that full backups to the DD200 Restorer are 41% faster than backups to tape. The data transfer rate for the DD200 Restorer was 63 MB/s (or 228 GB/hr), compared to 45 MB/s (or 158 GB/hr) for the LTO-2 drive. Time to Complete Full Backup Seconds DD200 Storage Units 306 LTO-2 Again, backups to disk do not require allocation of tape cartridges or tape drives, robotic movement, media mounting, media positioning, media offline, or media eject operations. These delays typically last from a few seconds to a few minutes. In the above testing, the delay caused by mounting a tape was approximately one minute. Increased backup performance allows IT organizations to complete backups within allowed backup windows and meet high availability requirements of business-critical applications. 10

11 DD200-TO-TAPE COPYING: 43% FASTER THAN TAPE-TO-TAPE COPYING With the DD200 Restorer as a NetBackup disk storage unit, making tape copies is much easier and faster. The DD200 Restorer can stream a high-end tape drive for best performance. Since backup images on the DD200 Restorer are not multiplexed; there is no need to demultiplex them during the tape duplication process. The DD200 Restorer allows data to be written to tape contiguously in order to speed up future restores. The following chart shows performance advantages of the DD200 Restorer for tape duplication: Time to Complete Tape Duplication Seconds DD200 to LTO-2 LTO-2 to LTO-2 The above testing measured the time it took to complete tape duplication. Duplicating the backup image on the DD200 Restorer to tape is 43% faster than duplicating the same image from one LTO-2 tape drive to another. Tape-to-tape duplication would have taken longer if the backup image needed to be demultiplexed or if the backup image spanned multiple tapes. 11

12 ON-SITE RECOVERY CAPACITY FOR RETAINING MONTHS OF BACKUPS Through its patent-pending Global Compression technology, the DD200 Restorer offers up to 23 TB of useable capacity. This allows the DD200 Restorer to easily retain two to five months of backup images to serve as the onsite recovery repository. This capacity ensures rapid recoveries while taking advantage of performance benefits of disk. In addition, the DD200 Restorer offers this capacity in a small footprint a 4U chassis that fits in a standard 19-inch rack. GLOBAL COMPRESSION: DISK-BASED DATA PROTECTION AT THE COST OF TAPE The Data Domain DD200 Restorer s Global Compression reduces the size of backup data by an order of magnitude or more in conventional use. This powerful compression functionality lowers the overall price-per-gb to be in the same range as tape automation. When Data Domain replication is used, it also reduces WAN bandwidth required for remote backup to be significantly lower than the best available block delta approaches. Global Compression pools redundant patterns within a file, across files, and even within a block, and stores only unique data segments. This compression algorithm aggressively minimizes the capacity needed for storing backup images. Global Compression is also data format independent. Thus, backup images can contain both structured data such as databases and unstructured data such as text files. To NetBackup, Global Compression happens behind the scenes. NetBackup simply writes to and reads from a large NFS or CIFS file system on the DD200 Restorer. With Global Compression, if data is retained longer on the DD200, the compression factor will increase. The first full backup will typically see about 3-4x compression; subsequent differential incremental backups will see 6-7x compression; subsequent full backups will see 50-60x compression. In a typical weekly full, daily differential incremental backup policy, this results in 20x aggregate compression after 12 weeks. Global Compression Benefits Description First full backup Differential incremental backups Subsequent full backups Compression Benefit 3 4x 6 7x 50 60x Aggregate for weekly full and daily incremental 20x backups (after 12 weeks) Aggregate for daily full backups (after 12 weeks) 80x+ The following illustrates the effect on storage capacity with Data Domain s Global Compression where 7.9 TB (or GB) of backup data was retained in the DD200 Restorer, taking up GB of physical storage. This yields a 21:1 compression ratio over two months. These results were seen at a leading software company, using VERITAS NetBackup to protect its Windows file server data. The dip in the top line was due to a retention period ending and a cycle of backups being deleted from the file system by NetBackup. 12

13 Data Domain Global Compression (Customer Example) Aggregate Storage Used (GB) /9/2004 3/16/2004 3/23/2004 3/30/2004 4/6/2004 4/13/2004 4/20/2004 4/27/2004 5/4/ :1 Aggregate Compression Useable (Pre-Compressed) Physical (Compressed) BENEFITS OF SYNTHETIC BACKUPS ON DATA DOMAIN DD200 RESTORER Synthetic Backups greatly simplify data recovery as the restore process requires fewer backup images. Because the synthesis process takes place on the NetBackup master/media server, Synthetic Backups do not impact the original NetBackup clients. Synthetic Full Backups are created from a traditional full backup and any number of subsequent incremental backups. The goal is to create a full backup image from existing backup data as though a full backup was performed at the time of the last incremental backup. The recovery process requires only a single backup image. Unique to NetBackup is the ability to create a Synthetic Cumulative Backup from a set of cumulative and differential incremental backups. The recovery process requires the last full backup image and a synthetic cumulative backup image. Furthermore, these Synthetic Cumulative Backup images can then be used to create a synthetic full backup image on a monthly or quarterly basis. 13

14 Traditional full backup to DD200 Restorer (Week1: Sun) Synthetic full backup to DD200 Restorer Current as of Sat No new data segments are saved on the DD200 Restorer Synthetic full backup to DD200 Restorer Incremental backups to DD200 Restorer (Week 1: Mon-Sat) Incremental backups to DD200 Restorer (Week 2: Mon-Sat) In the above scenario, a traditional full backup and subsequent incremental backups are directed to the Data Domain DD200 Restorer as a disk storage unit. Then these backup images are merged into Synthetic Full Backups and saved on the same DD200 Restorer. Synthetic Backups ensure a full backup image is available online for recovery operations. Using the DD200 Restorer as both the source and destination for Synthetic Backups can dramatically raise the usability and efficiency of Synthetic Backups. While synthesizing a backup, NetBackup processes the newest source images first, followed by sequentially older images. If two or more source images have been written to the same tape or if the source backup was multiplexed, the synthesis process will require multiple passes over the source tape media, slowing down the entire process. Thus, saving the original backups on the DD200 Restorer results in better performance in creating a Synthetic Backup. As the destination for Synthetic Backups, the DD200 Restorer also benefits from its unique Global Compression which stores only unique data segments. Because Synthetic Backups are created from existing backup images already saved on the DD200 Restorer, Synthetic Backups do not require additional storage. 14

15 HIGHLY RELIABLE, PROACTIVE VERIFICATION OF DATA RECOVERY One of the biggest challenges for tape is indeterminate backup quality. A backup process may have completed successfully but it is difficult to verify that the backup image on all of the tapes is recoverable. One bad tape can cause a restore operation to fail and this is often discovered at the worst possible time during a recovery. Disk-based backups can take advantage of RAID capabilities offered by the storage subsystem. However, the combination of Data Domain and VERITAS offer unprecedented levels of data integrity and reliability designed specifically for backup images to ensure recoverability. DATA DOMAIN DATA INVULNERABILITY ARCHITECTURE Data Domain s reliability goes beyond RAID protection. Neither ATA RAID nor tape provides this level of built-in, redundant data protection. The Data Domain Data Invulnerability Architecture protects against data loss from hardware and software failures at multiple layers: When writing to disk, the DD200 Restorer creates and stores self-describing metadata for all data received. After writing the data to disk, the DD200 Restorer recreates metadata from the data on the disk and compares it to the original metadata. Data Domain s log structured file system is designed specifically for backup and recovery. Backup images are written (for backups), read (for restores or duplications), and deleted (for expired backup images) but typically are not modified. Therefore, unlike traditional file systems, Data Domain s append-only file system ensures that valid data is never accidentally overwritten; valid data is safe once it is on disk. After a backup completes, a validation process ensures that all of the data can be read back. In the background, proactive integrity and consistency checks continuously verify that backup images are readable and can be restored. The disks in the DD200 Restorer are set up in a mirrored configuration (RAID1+ 0) with hot spares and a fast mirror resynchronization capability. To keep data synchronized during a hardware or power failure, the DD200 Restorer uses NVRAM (non-volatile RAM) to track outstanding I/O operations. When reading data back for a restore operation, the DD200 Restorer uses multiple layers of consistency checks to verify that the restored data is correct. If errors are detected at any level, the DD200 Restorer can self-heal from metadata and error-correcting codes stored within the system. In many cases, errors are repaired online and error corrections are noted in the DD200 Restorer s log. In rare cases where the DD200 Restorer s file system needs to be unmounted for repair, the DD200 Restorer will send out an alert via so that the administrator can plan for maintenance. VERITAS NETBACKUP MEDIA VERIFICATION OPTION VERITAS NetBackup provides the media verification option for the contents of a backup. The verification option reads the backup media and compares its contents to what is recorded in the NetBackup catalog. Although this operation does not compare the data on the media with the contents of the client disk, it does read each block in the image to verify that the backup image is readable. Tape-based backups do not take advantage of this option effectively since the operation can disrupt already scheduled backups by creating tape resource contention. The media verification operation for backup images on the DD200 Restorer will no longer create resource contention since disk storage units allow simultaneous accesses. 15

16 The combination of NetBackup s media verification and Data Domain s Data Invulnerability Architecture ensures reliable and successful data recoveries. SIMULTANEOUS ACCESS TO DATA DOMAIN DD200 RESTORER NetBackup enable up to 256 simultaneous read and write operations to a disk storage unit on the DD200 Restorer. This provides several benefits including: SIMULTANEOUS BACKUPS, RESTORES, AND DUPLICATIONS Backups, restores, and duplication operations can be performed simultaneously on the DD200 Restorer. NetBackup places no limitations with regard to the number of simultaneous backup, restore, or duplication jobs, as long as the Maximum Concurrent Jobs parameter is not exceeded. If backups are running when an urgent restore request is issued, the restore request is fulfilled immediately without pausing the backup process. With a tape drive, the backup tape must be unloaded and the restore tape(s) must be loaded. Only when the restore process is finished (which may take minutes to hours), the backup job can continue. In addition, there is no need to leave a tape drive idle or dedicated for recovery purposes, making better use of the tape investments. USER-DIRECTED RESTORES WITHOUT IMPACTING REGULARLY SCHEDULED BACKUPS The flexibility for simultaneous access also allows IT organizations to make better use of existing VERITAS NetBackup features such as the media verification option and user-directed backup and restores. NetBackup allows client users to initiate backup, archive, and restore operations for their systems without operator or administrator intervention. These user-directed backups allow the user to protect their files immediately on demand. This feature, however, is not widely enabled since user-driven backups and restores can disrupt already scheduled backups or urgent system-level restores by creating tape resource contention. With the disk storage units along with the DD200 Restorer, users can restore their own files without these negative effects. This reduces administrative requirements when users need to recover files that were accidentally deleted or damaged. IMPROVED DISASTER RECOVERY CAPABILITIES FOR OFFSITE ARCHIVES The combined solution enables IT organizations to leverage investments in the existing tape infrastructure to create long-term archives or disaster recovery copies. VERITAS NetBackup provides several ways to create tape copies from the Data Domain DD200 Restorer. This reduces the time for the backup and recovery process and leverages portability benefits of tape. 16