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-------------------------------------------------------------- This story was printed from ZDNet Australia. --------------------------------------------------------------
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Tape backup: 9 drives tested August 07, 2003 URL: http://www.zdnet.com.au/reviews/hardware/storage/soa/Tape-backup-9-drives-tested/0,139023427,120274227,00.htm
  With storage capacities growing by leaps and bounds, the need for effective backup is even more important. We look at your options.
The primary purpose for a tape drive is to store and back up data. By installing a tape drive with removable media, data can be physically stored away from your machine. Should your computer become unusable, your critical data files can reliably be retrieved with a minimum of effort. There are many different strategies for protecting data, which brings on the debate about tape vs disk. Tape however still represents the most logical and cost-effective solution. Tape vs Disk
Tape is essential in data protection for the following reasons:
Generally with less mission-critical situations you would use tape; the more important the data is, the more likely it is you would choose disk. However, having a combination of these two technologies can ensure that all the bases are covered. Storage requirements Picking the right solution to best meet your business needs may mean having a mixture of different solutions. For this review we were only concerned with standard tape storage devices. The Quantum DX30, which we also tested, would sit in either the business-critical or mission-critical storage set. Deployment You should consider your current and future data requirements in terms of performance, capacity, and the backup window. Backup windows have shrunk as many enterprises that have gone global have become increasingly dependent on transaction-oriented systems. So to remain competitive, they can't afford to take key systems offline for too long. You will also need to look at scalability. Is it a proven technology that you are buying? Some drives have been around for years and their manufacturers continue to provide us with helpful roadmaps. There are technologies like DDS, which are reliable and widely used that don't have any future roadmaps. Expanding these systems will require more hardware since an increase in capacity is unlikely to emerge. It is also important to evaluate your choice of backup software as there are many specific features that can enhance your backup process. Some of the more popular packages out there include Veritas Backup Exec, Veritas Net Backup (64 bit, High-End), Computer Associates, and ARCserve. Let's look at the various tape formats. Tape formatsLTOLinear Tape-Open (LTO) is an open format technology that was jointly developed by HP, IBM, and Seagate. The "open format" means that tapes and drives from different manufacturers are compatible with each other. LTO uses linear multi-channel bi-directional tape formats and includes enhancements in the areas of timing based servo (error correction), hardware data compression, and track layouts. There are two formats based on the LTO technology: Accelis and Ultrium. The first generation of Ultrium allowed for storage of up to 100GB of data (>200GB compressed) on a single cartridge. The Accelis format utilises all the advantages of LTO except that the capacity has been reduced to improve access times to data. Ultrium Generation 1: Capacity 100GB native, 200GB compressed; Transfer Rate 20 to 40MBps compressed. Ultrium Generation 2: Capacity 200GB native, 400GB compressed; Transfer Rate 40 to 80MBps compressed. Accelis Generation 1: Capacity 25GB native, 50GB compressed; Access Time < 10 sec, Transfer Rate 20 to 40MBps compressed. DAT DDS-1: Capacity 2GB native; transfer rate 0.55MBps. DDS-2: Capacity 4GB native, 8GB compressed; transfer rate 1.1MBps compressed. DDS-3: Capacity 12GB native, 24GB compressed. DDS-3 uses PRML (Partial Response Maximum Likelihood), which eliminates electronic noise; Transfer Rate 2.2MBps compressed. DDS-4: Capacity 20GB native, 40GB compressed; transfer rate 4.8MBps compressed. A DDS cartridge needs to be retired after 2000 passes or 100 full backups and every 24 hours you should clean your drive with a cleaning cartridge and discard the cleaning cartridge after 30 cleanings. DDS tapes have an expected life of at least 10 years. DLT DLT 7000: Capacity 35GB native, 70GB compressed; transfer rate 20MBps compressed. SDLT 220: Capacity 110GB native, 220GB compressed; transfer rate 22MBps compressed. SDLT 220: Capacity 160GB native, 320GB compressed; transfer rate 32MBps compressed. AIT AIT-1: Capacity 35GB native, 90GB compressed; transfer rate 10MBps compressed . AIT-2: Capacity 50GB native, 130GB compressed; transfer rate 15.6MBps compressed. AIT-3: Capacity 100GB native, 260 compressed; transfer rate 31.2MBps compressed. SAIT-1: Capacity 500GB native, 1.3TB compressed; transfer rate 78MBps compressed. VXA VXA-1: Capacity 33GB native, 66GB compressed; transfer rate 6MBps compressed VXA-2: Capacity 80GB native, 160GB compressed; transfer rate 12MBps compressed. Mammoth Exabyte's Mammoth-2 drive uses a new multichannel helical scanning head, the latest error-correction algorithms and offers a 2.5:1 compression ratio using ALDC (Adaptive Lossless Data Compression). Mammoth-1: Capacity 20GB native, 40GB compressed; transfer rate 6MBps compressed. Mammoth-2: Capacity 60GB native, 150GB compressed; transfer rate 30MBps compressed. Travan TR-5 (NS-20): Capacity 10GB native, 20GB compressed; transfer rate 1.83MBps compressed. TR-7: Capacity 20GB native, 40GB compressed; transfer rate 4MBps compressed. Automated backup Tape libraries: With rapidly growing data capacities to consider to handle backup for client servers, many organisations opt for off-line data storage with automated access and control. A "tape library" is a high-capacity data storage system used to store, retrieve, read, and write data using multiple magnetic tape cartridges. Essentially, it is made up of two pieces of hardware: the tape drive itself plus the robotics used to manipulate the tapes. Robotic arms select tape cartridges from built-in storage racks and load them into the drive when required by the backup software. When the cartridges are full, or are no longer needed, the arm puts them back in the library. Tape library units may have several drives for simultaneous reading and writing and may hold from a few to hundreds of cartridges. Larger units can have hundreds of drives and store several thousand cartridges. These devices are referred to as "near online" devices because they are not as fast as on-line hard disks. Tape arrays: Tape arrays are built around technology normally used with disk-based RAID subsystems. Arrays use special controllers that can stripe data across multiple drives in parallel, as opposed to the slower method of using sequential access on a single device. For extra fault tolerance, most tape arrays can be configured with a parity drive. The downside is a decrease in overall throughput gains. Hierarchical storage management: HSM applications have been developed in an effort to minimise storage costs while optimising performance. They do this by combining multiple storage media such as magnetic disk, optical disk, and tape into a single logical unit, and transparently migrating data between media based on access frequency. Tape drivesExabyte VXA-2 (internal)
HP Ultrium 460 
Lynx LTO 460 
More tape drivesLynx VXA-2
Lynx VXA-2 
Quantum DLT VS80 
Even more tape drivesQuantum SDLT-320
Seagate Viper 200 
Sony AIT SDX-D700B 
Specifications
Test results
How we testedâ€"tape drivesOur test server was an Acer Altos 1200; it was equipped with the following:
This is a typical mid-range server that one would most likely use with the tape devices we tested. To really get the best out of the Ultrium 2 drive, for example, you would need to spend thousands on a high-end disk array to get the 30MBps transfer rates that can be achieved using an Ultrium 2 drive. For our backup software we chose Veritas Backup Exec for Windows NT/2000 Version 9.0, Build 4367. The software was configured to carry out full copies of the data, ignore the archive bit, perform no verify, and use hardware compression if available. During restore the directories concerned were deleted from the server's hard drive and the software configured to overwrite all files. The data backed up to the units during testing totalled 20,631,422,036 bytes and comprised 71,108 files and 6476 folders. We then restored a smaller folder that totalled 4,207,894,052 bytes and comprised 7144 files and 1004 folders. All times were taken from the Veritas -Activity Monitor"â€"this included rewind times at the end of the operation, for example. The results were tabulated and from the backup times an average transfer speed for each drive was calculated. We also rated each of the tape back up units in the areas of interoperability, future proofing, return on investment and service. Interoperability: Software support across the platforms. (eg, Windows) Futureproofing: With futureproofing we were predominantly concerned with capacity in terms of native and compressed storage capacity. We also looked at the transfer speeds in MBps. Return on Investment: We looked at the initial purchase price of the unit as well as the cost per GB. Service: With service we looked at the length of the warranty as well as the types of services offered (eg, on-site exchange, RTB). ScenarioCompany: Hood AustraliaThis company wants to back up a variety of servers to a single highcapacity tape drive. Approximate budget: $10,000 (drive cost) Requires: One backup drive with at least 100GB raw capacity per tape. Drive must be external and connect using SCSI. Concerns: Speed of backup is the primary concern, while cost of backup tapes is also an issue. Best Solution: The Lynx LTO 460 takes out the Editors' Choice Award. It was the fastest of all the drives tested and it featured the highest cartridge capacities. Even though its initial purchase price is high, the cost per gigabyte is very low. The Quantum SDLT-320 also deserves a worthy mention. It's fast and its initial price is relatively low. It doesn't use a new tape format like the Lynx LTO 460 and it features downward compatibility with tapes using DLT technology. What to look for when buying a tape backup unit:
About RMIT Test Labs
RMIT IT Test Labs is an independent testing institution based in Melbourne, Victoria, performing IT product testing for clients such as IBM, Coles-Myer, and a wide variety of government bodies. In the Labs' testing for Technology & Business, they are in direct contact with the clients supplying products. Their findings are their ownâ€"only the specifications of the products to be tested are provided by the magazine. For more information on RMIT, please contact the Lab Manager, Steven Turvey.
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