Why Choose Native Fibre Channel Backup? Optimal protection for the SAN

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1 Exabyte Corporation th Street Boulder, CO EXABYTE An Exabyte White Paper Why Choose Native Fibre Channel Backup? Optimal protection for the SAN Lynda Edgington Exabyte Technical Publications Executive summary For years, SCSI-based tape drives and tape libraries have provided effective backup for traditional business networks. These networks employ server-attached storage disks attached to the network through servers that control the data. Backing up server-attached storage typically involves sending data across the network to tape libraries attached to backup servers. These massive data transfers degrade network performance and prevent servers from concentrating their resources on other business processes. Traditional server-attached storage is rapidly giving way to storage area networks (SANs). Businesses are adopting Fibre Channel SANs to alleviate the data storage and delivery problems associated with ever-increasing data loads. SANs provide data availability, shareability, and manageability that is not possible with server-attached storage. Businesses making the switch to SANs are finding that they have a tremendous opportunity to upgrade their backup operations. By attaching Fibre Channel tape drives and libraries directly to the SAN, a business can back up its network more quickly, eliminate network slowdowns during backups, make more efficient use of backup resources, and simplify backup and recovery administration. Exabyte provides leading-edge native Fibre Channel tape drives and libraries that attach directly to the SAN without the use of intervening routers. Exabyte libraries, featuring Mammoth-2 (M2) tape drives, support serverless backup in which data can be moved directly from disk to tape without the involvement of a server. With Exabyte s native Fibre Channel backup devices, your backups can finally be completely transparent to users and processes on your network. July 2001 CS

2 Why Choose Native Fibre Channel Backup? July 2001 Businesses are scrambling for computing solutions that can manage extreme data loads with unprecedented speed and accuracy. Where we are today When asked to name the most important factor affecting today s business computing decisions, IS professionals have an immediate reply: explosive data growth. Businesses are scrambling for computing solutions that can manage extreme data loads with unprecedented speed and accuracy. With our increasing reliance on such applications as internet commerce, enterprise resource planning, and on-line transaction processing, the requirements are clear: Data must be available cross-platform, cross-application, without delay, and without error. To meet these requirements, Fibre Channel storage area networks (SANs) have emerged as the top solution for delivering data. Fibre Channel is a standard for information delivery that enables large data transfers at very high speeds with minimal network protocol overhead. A SAN is a Fibre Channel network that is separate from a business s regular network. The SAN is dedicated to storing, backing up, and delivering data to and from users, servers, and storage devices. SANs speed up data delivery, allow more efficient use of storage resources, and simplify data management. You may be in the process of implementing a SAN for your business, or you may be evaluating such a move. We will discuss the many benefits of SANs later in this paper. For now, we will focus on a specific aspect of network management: the dreaded data backups. As you will see, if you are in the process of moving to a SAN to alleviate your storage problems, you can reap the added benefit of no-hassle backups by employing Fibre Channel backup devices on your SAN. The backup picture There is no question that backups are essential for data-intensive businesses. Operating without a backup strategy means risking everything. Tape backup is a proven technology that is cost-effective and reliable. That s why most businesses employ tape drives or tape libraries to back up critical data. If your business network is like most, you probably have a well-established Ethernet-based system connecting your users with application servers, file servers, and each other. Your network includes various servers dedicated to specific business processes, like resource planning, transaction processing, accounting, , and such. These servers typically have their own dedicated server-attached storage disks attached directly to the server. Page 2 of 12

3 July 2001 Why Choose Native Fibre Channel Backup? Initially, you may have met your backup needs by connecting a SCSI-based tape drive or small tape library to each server to back up that server s disks. This is traditional server-attached backup. As the amount of data and number of servers increased, you probably consolidated your backups by attaching a larger library to a dedicated backup server and sending data across the network to be backed up. Do backups give you nightmares? As critical as backups are to business, they are arguably the least-loved aspect of network administration. Backups are notorious for bogging down networks. As data volumes increase, network delays during backups are reaching unacceptable levels. Most network protocols in use today were designed for infrequent transfers of small files and the exchange of instructions between users and processors. When handling large amounts of data, these protocols introduce significant overhead. During backups, networks suffer not only from traffic volume, but from data transfer inefficiencies. As data volumes increase, network delays reach unacceptable levels. In addition to causing network slowdowns, backups also monopolize servers. During backups, servers must devote a high percentage of their processing power to pulling data from network disks and sending it to tape drives. These servers are prevented from devoting their full resources to other important business applications. To avoid these problems, you try to schedule your backups for off-hours or weekends. However, if you are a 24x7 business, there may be no appropriate down-time for backups. You may be forced to accept routine sluggish network performance, or you may be backing up less often than you would like to avoid slowing down business. As if squeezing backups into an ever-shrinking backup window isn t hard enough, you have to deal with managing all of the backup systems scattered throughout your network. You have to visit multiple locations and use a variety of software packages to set backup schedules. You have to verify that backups complete and you must collect tapes. You have to perform routine maintenance and troubleshoot problems. And, with constantly increasing data volumes, you frequently have to install new backup devices and reconfigure servers to support them. The ultimate aggravation is that you are devoting significant resources to keeping your backups running resources that are doing nothing to enhance the performance of your network. Page 3 of 12

4 Why Choose Native Fibre Channel Backup? July 2001 Why do we do this? We continue to put up with backup nightmares because server-attached backup has been the only effective option for years. SCSI-based backup devices have served us well in server-attached configurations because SCSI is ideal for transferring data between two devices over short distances. SCSI supports large data transfers and offers extremely fast transfer rates (currently up to 160 MB/second). These capabilities are exactly what is needed for server-attached backup. However, businesses are finding that data has reached a critical mass that threatens to bring down the network unless a new approach is found. As server-attached storage gives way to SANs, backup strategies must also evolve to keep pace with the benefits provided by the SAN. SANs offer businesses a way to solve their data storage, management, delivery, and backup problems. Businesses are turning to SANs Over the past few years, SANs have evolved from a concept promising great benefits to a rapidly-maturing technology embraced by many businesses. SANs offer businesses a way to solve their data storage, management, delivery, and backup problems. Some of the dramatic benefits of SANs are: Quicker data delivery. Data transfers take place on the Fibre Channel SAN rather than the production network. Fibre Channel currently transfers data at 100 MB/ second. In the near future, speeds of 200 and 400 MB/second will be common. In comparison, widely used 100BaseT Ethernet transfers data at approximately 10 MB/ second. Better network performance. Network slowdowns are eliminated because the SAN frees the production network from the task of transferring huge amounts of data. More efficient use of storage. Storage is not tied to specific servers, so it becomes a pooled resource. Storage can be allocated as needed, resulting in less under-use or over-use of individual storage devices. Increased data accessibility. Data can be shared among all servers attached to the SAN. Fibre Channel allows multiple devices to access the same data, regardless of platform, physical interface, operating system, or data protocol. Easier scalability of storage. An administrator can hot-plug additional storage into the SAN as needed, without having to bring down the network or reconfigure servers. Page 4 of 12

5 July 2001 Why Choose Native Fibre Channel Backup? Improved fault tolerance. Multiple data pathways, mirroring capability, and reduced error rates provide a highly reliable data transfer system. If a server or data path fails, alternate routes through the SAN are available. Improved storage manageability. An administrator can monitor and control all of the SAN s storage from a single remote console. How does a SAN improve backups? While SANs are deployed primarily to remedy data storage problems, tremendous benefits also come in the area of data backups. These benefits parallel those just mentioned. Quicker backups With tape libraries attached directly to the SAN, data to be backed up is sent through the SAN rather than the production network. Backups take place more quickly because the Fibre Channel SAN moves data much more quickly than the typical Ethernet-based network. If the SAN supports serverless backup (described on page 9), backups can take place even more quickly because server bottlenecks are eliminated. Better network performance With data moving across the SAN rather than the production network, the network no longer bogs down during backups. Backups can take place at any time without impacting network users. More efficient use of backup resources Backup resources are used more efficiently because capacity can be shared among all the devices on the SAN. Because storage is no longer tied to specific servers, data can be directed to any backup device on the SAN that has the appropriate capacity. Greater accessibility to data for recovery Because storage devices aren t tied to particular servers, data recovery doesn t have to be tied to a particular server s backup device. Just as backups can be sent to any tape drive on the SAN, recovery can take place from any tape drive. The data is simply directed through the SAN to the affected storage device. Tapes can be managed at a central location, and recovery can be controlled from a single console. Page 5 of 12

6 Why Choose Native Fibre Channel Backup? July 2001 Easy scalability When additional backup resources are required, an administrator can hot-plug devices into the SAN without reconfiguring servers. Unlike the limited number of devices supported on a SCSI bus, the SAN can support enough backup capacity to meet the needs of the entire network. The most common Fibre Channel networks implemented today can support over a hundred devices. The Fibre Channel standard defines other configurations that can support thousands to millions of devices. Improved fault tolerance Backup operations are more fault tolerant on a SAN because Fibre Channel provides multiple pathways for data. If a data path fails, data can be routed through a different data path. Likewise, if a tape drive fails, data can be backed up to another tape drive on the SAN. For additional fault tolerance, data can be copied to multiple devices on the SAN, including devices at remote sites. Depending on the type of cabling used, data can be transferred up to 10 kilometers (6.2 miles) between Fibre Channel devices, allowing direct remote data duplication. Simplified backup management The management of backups is much easier because backup devices can be centrally located and monitored from a single console. Because backup resources are used more efficiently, there are fewer devices to monitor and maintain. Because resources are pooled, they can be easily allocated as needed through software. True native Fibre Channel connectivity and serverless backup support make the Exabyte 430M, X80, and X200 ideal for backing up the SAN. Fibre Channel backup from Exabyte Exabyte has always understood the importance of providing cost-effective, reliable backup solutions. With the emergence of SANs, these solutions must also integrate seamlessly into the Fibre Channel network. With SAN applications in mind, Exabyte has introduced three native Fibre Channel libraries. The 430M, X80, and X200 MammothTape libraries, shown in Figure 1, feature Exabyte s award-winning native Fibre Channel M2 tape drives. Each library and its tape drives connect directly to the Fibre Channel SAN without the need for intervening routers. The M2 tape drive is the first midrange tape drive with native Fibre Channel connectivity, as well as the first in its class to provide built-in serverless backup support. Serverless backup, described on page 9, allows backups to proceed directly from disk to tape without server involvement. True native Fibre Channel connectivity and serverless backup support make the 430M, X80, and X200 ideal for backing up the SAN. Page 6 of 12

7 July 2001 Why Choose Native Fibre Channel Backup? The Exabyte 430M Library 4.5 TB capacity (compressed) 432 GB/hour transfer rate (compressed) Up to four M2 tape drives Up to 30 tapes Standalone or rack-mountable Supports serverless backup The Exabyte X80 Library 12 TB capacity (compressed) 864 GB/hour transfer rate (compressed) Up to eight M2 tape drives Up to 80 tapes Standalone or rack-mountable Supports serverless backup The Exabyte X200 Library 30 TB capacity (compressed) 1 TB/hour transfer rate (compressed) Up to ten M2 tape drives Up to 200 tapes Standalone or rack-mountable Supports serverless backup Figure 1 Exabyte s SAN-ready native Fibre Channel libraries Page 7 of 12

8 Why Choose Native Fibre Channel Backup? July 2001 Native vs. non-native Fibre Channel The importance of native Fibre Channel for effective SAN backup cannot be overemphasized. The benefits discussed in this paper rely on backup devices being connected directly to the SAN. When Fibre Channel SANs first came into being, an effort was made to enable tape drive and library owners to connect their SCSI-based backup devices to the SAN. This led to the development of SCSI-to-Fibre Channel routers that translate device mapping and addressing protocols between the two interfaces. SCSI-to-Fibre Channel routers are less than ideal for effective backup in mature SAN environments. SCSI-to-Fibre Channel routers were useful in early SAN implementations because they allowed users to experience many of the benefits of SANs without having to scrap expensive backup equipment. However, these routers have a number of drawbacks that make them less than ideal for effective backup in mature SAN environments: Routers cause performance bottlenecks. When multiple tape drives in a library are connected to the SAN through a router, all of the data to and from the drives passes through just one or a few Fibre Channel connections. Forcing what should be multiple data streams into a fewer than optimum number of channels makes it difficult to use the full streaming capability of each tape drive. Routers introduce potential failure points. When a library and its tape drives are connected to the SAN through a router, failure of the router takes the entire library and its drives out of service, even when they are functioning perfectly. Routers are difficult to configure. An administrator must work with complex address mappings to assign multiple SCSI IDs to a single Fibre Channel connection. In addition, the router must be reconfigured each time a new device is added. Routers aren t scalable. A library s capacity can be expanded by adding tape drives, but if the router s total bandwidth is already in use, the router must be replaced to accommodate the additional drives. Routers are expensive. Routers can cost well over $10,000. As SAN administrators routinely upgrade their backup systems, they are turning to native Fibre Channel systems that eliminate the need for routers. Without the router, library and tape drive performance is used more effectively because data no longer has to pass through a fewer than optimum number of Fibre Channel connections. When connected through a hub, multiple drives in a Fibre Channel library can be kept streaming (up to the hub s data rate limit). When connected through a switch, all of the drives in a library can easily be kept streaming. With a library connected directly to the SAN, the potential failure point at the router is eliminated. Failure of this single piece of equipment can no longer take out the entire library. Page 8 of 12

9 July 2001 Why Choose Native Fibre Channel Backup? Library capacity and performance can be expanded by simply adding new drives, without the configuration hassles of a router. Drives can be hot-plugged into the library without interrupting library or SAN operations. Note that while some tape libraries claim to be native Fibre Channel, they really just contain an integrated router. If the internal router fails, the entire library and its drives are out of commission. The router cannot simply be swapped out, so repair is expensive and time-consuming. True native Fibre Channel libraries from Exabyte eliminate the router failure point and provide enhanced reliability, throughput, and cost-effectiveness for the SAN. Serverless backup removes the server bottleneck Even though backups are quicker on the SAN, data does not flow optimally between storage and backup devices because servers are involved. Without question, sending backups through a SAN relieves networks of the problems associated with massive data transfers. However, even on a SAN, most backup systems require servers to process the data transfers. The server itself becomes a bottleneck as data moves from disks on the SAN to server memory, then from server memory to tape drives on the SAN. Even though backups are quicker on the SAN, data still does not flow optimally between storage and backup devices because servers are involved. In addition to the performance bottleneck, managing data transfers during backups prevents servers from using their full resources on other important tasks, such as running applications and processing data. As a result, although the backup window is not as tight as it was before the SAN, it still exists. Backups must still be scheduled when they have the least impact on users and business processes running on the servers. Exabyte s M2 tape drive eliminates these performance impediments by providing built-in serverless backup, a process by which data goes directly from disk to tape on the SAN, without traveling through a server. Serverless backup is sometimes called extended copy or E-copy because it is based on the SCSI Extended Copy command. As shown in Figure 2, a server simply issues an Extended Copy command to the tape drive through its application software. The command specifies the data s location and how much is to be transferred. The tape drive then assumes control of the actual data movement between disk and tape. With serverless backup, network administrators see significant cost-saving benefits above and beyond those already achieved through the SAN: Backups occur more quickly since server bottlenecks no longer exist. Dedicated backup servers can be eliminated. Application and file servers that double as backup servers can be made fully available for other business-critical tasks. Page 9 of 12

10 Why Choose Native Fibre Channel Backup? July 2001 Bypassing the server boosts backup performance, eliminates backup window constraints, and allows servers and backup devices to be used more efficiently. Tape drive speed is better utilized because data can be streamed directly to tape instead of being held up by server performance limitations. Backups can take place at any time without impacting the network or servers, completely eliminating the concept of a limited backup window. Data recovery is quicker because frequent snapshots of the network are more convenient to perform; backup tapes contain more recent versions of data, so there is less work to recreate and business can resume more quickly. Local Area Network Server 1 Server issues Extended Copy command across SAN to tape drive 2 Tape drive instructs disks to read and send data Disks Fibre Channel switch Tape drive 3 Disks send requested data across SAN to tape drive 4 Tape drive writes data to tape Figure 2 Serverless backup between disks and a tape drive on a Fibre Channel SAN Be aware that some tape systems implement serverless backup by attaching a storage router that manages the data movement between the SAN and the tape drive. Exabyte s M2 is the first tape drive to offer built-in serverless backup support. The router an expensive piece of equipment that is a potential point of failure and a source of performance bottlenecks is unnecessary. Page 10 of 12

11 July 2001 Why Choose Native Fibre Channel Backup? Even if you don t have a SAN, SCSI limitations may make Fibre Channel a better choice for your backup systems. What if you aren t ready for a SAN? If you re not quite ready to implement a SAN, should you stick with SCSI or move to Fibre Channel when you need to add more backup resources? While SCSI is a well-established, reliable standard for backup devices, you may find that SCSI backup is no longer sufficient for your expanding network. SCSI limitations on distance between devices, number of devices supported, and bandwidth shareability may make Fibre Channel a better choice for your backup systems. Distance between devices SCSI is capable of high data transfer rates (up to 80 MB/second for Ultra2 SCSI and 160 MB/second for Ultra3), but these rates can only be achieved over short distances (up to 12 meters for multiple devices). Fibre Channel can support distances of up to 10 kilometers between devices while still providing high data transfer rates (100 MB/second now, 200 and 400 MB/second in the near future). The distance capabilities of Fibre Channel not only facilitate remote backup, but open up options for the placement of backup devices within a business facility. Number of devices The maximum number of devices that can be connected to a wide SCSI bus is 16. This inhibits sharing of tape libraries between servers because a large library and its drives may use up most of the available SCSI IDs. The basic Fibre Channel configuration, an arbitrated loop, can support up to 126 devices, and switched fabrics can support millions of devices. Even without a SAN, you can easily share a Fibre Channel tape library among multiple servers and their disk systems. Bandwidth shareability All of the devices on a SCSI bus must share the bandwidth of the bus. This means that all of the tape drives in a library may be competing for bus access at the same time. When multiple devices are attached to a SCSI bus, complex arbitration and addressing protocols are required to control bus access and manage data flow. The processor overhead required to manage the bus degrades the performance of all the devices on the bus. In contrast, Fibre Channel provides greater bandwidth with simpler arbitration and addressing protocols. In a Fibre Channel arbitrated loop, tape drives take turns as on a SCSI bus, but access to the bandwidth is more efficient. In a switched fabric, all of the tape drives in a library can use the full bandwidth of Fibre Channel simultaneously. Page 11 of 12

12 Conclusion July 2001 Look to Fibre Channel for backup If the volume of data on your network is expanding rapidly, as it is on nearly all networks, consider phasing in Fibre Channel backup devices even if you aren t ready for a SAN. Many servers that control large disk systems either already have Fibre Channel interfaces or are upgradeable to Fibre Channel through the addition of host bus adapters. You can connect a standalone Fibre Channel M2 tape drive directly to the server, or you can connect a Fibre Channel library through a hub or switch. Whether or not you are contemplating a SAN, Fibre Channel backup devices will serve you well in your present situation and can be easily integrated into a future SAN if you choose to go that route. Copyright 2001 by Exabyte Corporation. All rights reserved. Exabyte, Exabyte Recognition System, Exafacts, Exapak, Exasoft, Exatape, and Strategex are U.S. registered trademarks of Exabyte Corporation. Eliant, M2, MammothTape, NetStorM, SmartClean, and SupportSuite are U.S. trademarks of Exabyte Corporation. All other product names are trademarks or registered trademarks of their respective owners. Conclusion Fibre Channel SANs are rapidly emerging as the architecture of choice to meet the data delivery requirements of today s businesses. SANs greatly improve data availability, shareability, and manageability over traditional networks that use server-attached storage. Businesses that implement a SAN save a significant amount of money through more efficient use of storage resources, greater productivity, and reduced administrative costs. As on any network, backup on the SAN is essential. While backups on a traditional network can cause considerable headaches, backups on the SAN are pain-free. With a SAN, Backups take place more quickly The impact of backups on network performance is eliminated Tape drives and libraries are used more efficiently Data is more accessible for recovery Backup capacity can be added easily Fault tolerance during backups is increased Backups are easier to manage The key to effective SAN backup is attaching tape drives and tape libraries directly to the SAN. While SCSI tape drives and libraries can be attached to the SAN through routers, backup devices need native Fibre Channel interfaces to avoid creating data bottlenecks and bringing unnecessary complexity and cost to the SAN. Exabyte is the first company to integrate a native Fibre Channel interface into its tape storage devices. The 430M, X80, and X200 libraries with M2 tape drives attach directly to the SAN without intervening routers. These libraries are also the first to support serverless backup, which eliminates server bottlenecks, allows server resources to be applied to other processes, and makes the concept of a limited backup window obsolete. Exabyte designs its libraries with the reliability, scalability, and manageability required for storage area networking. With native Fibre Channel and serverless backup support, the 430M, X80, and X200 libraries provide optimal protection for the valuable data on your SAN. Page 12 of 12