Technology Report: WORM Tape


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Archive with WORM tape

WORM Field Report
We recently spoke with John Lowe, associate

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vice president, network systems engineering, at investment firm Morgan Keegan & Co. Inc. about his WORM tape system.

Q: What type of WORM tape system do you have?
A: We have a Spectra Logic 64K AIT3 in our main data center and a Spectra Logic 20K AIT3 in our business continuity center.

Q: How much data is currently stored on WORM tape?
A: We have 3TB.

Q: WORM tape offers a cost-effective solution that helps satisfy regulatory requirements. What do you use it for?
A: We use the WORM tape library for the SEC's rule 17a-4, and for e-mail, instant messaging and fax archiving.

Q: Did you consider disk or software products before you purchased your WORM tape library?
A: Yes, we considered disk and other solutions in late 2002 and early 2003; although vendors promised compliance, the government was silent on their acceptance of anything other than optical or WORM tape.

Q: What kind of system did you put in place to make sure your cartridges are WORM, and not just plain tape?
A: We use a tape library partitioned for WORM only. The media is logically and physically separate from the backup media, and we only use approved WORM media.

Q: How are your WORM tape policies different from your regular tape backup policies?
A: Retention periods are set at three years, and destruction policies and procedures are enforced.

Q: What kind of application in addition to your regular backup software do you use to set retention policies for your WORM tape?
A: We use DiskXtender 2000.

Q: What do you like most about your WORM tape system?
A: It's hands-off and it's easy to manage and replicate media. We don't have to physically move media, and there's enough capacity in the library to meet retention requirements. Also, we can expand capacity on demand by adding additional drives and media.

Q: What do you like least?
A: The volatile nature of tape. Even though media storage is rated at 10-plus years, I probably wouldn't use it if retention periods were over five years.

Keep it all. That's increasingly the company line handed down by management to storage administrators. With sometimes conflicting and overlapping government regulations about retaining sensitive data within organizations, no longer can any data be viewed as disposable. More often than not, storage administrators end up storing everything, with a growing number examining write once, read many (WORM) tape as a method for satisfy long-term data retention requirements.

However, it's important to consider how, when and under what circumstances to deploy WORM tape. Tape is the newcomer to the world of WORM media, following on the heels of optical and disk. Changes to the tape cartridge and firmware upgrades to existing tape drive media now enable WORM functionality on tape. But before deploying this new technology, make sure WORM tape satisfactorily addresses issues such as security, durability, portability, performance, content management, disaster recovery and TCO. Many users will find that a properly designed WORM tape implementation offers a viable, cost-effective solution that helps them satisfy their regulatory requirements.

WORM tape benefits
WORM tape gives users the ability to store petabytes of unalterable data for decades at a fraction of the price of even the cheapest disk without having to make significant changes to their existing infrastructure. It comes with all of tape's features such as portability, recoverability and infinite capacity, and the list of tape vendors offering support of WORM technology continues to grow.

Storage Technology Corp.'s (StorageTek) 9840/9940 and Sony Electronics' AIT/SAIT tape families have offered WORM technology for years, while WORM support for IBM Corp.'s 3592 and Quantum Corp.'s DLT tape families was announced in May and June of 2004, respectively. Shops with LTO tape need to wait until the LTO consortium can hammer out a WORM LTO standard. However, LTO tape libraries can now use SAIT WORM tape. Current SAIT tape drives and cartridges have been retrofitted to fit into tape drive slots on LTO tape libraries. The WORM tape cartridges cost approximately 10% more than regular tape cartridges.

The benefits of WORM tape show up in its ability to use existing resources and processes with minimal additional expenditures. However, differences exist between regular and WORM tape cartridges:

  • WORM cartridges and cartridge labels are different colors. IBM's new 3592 WORM tape cartridges will be colored grey to enable tape handlers to easily distinguish between regular and WORM tape cartridges. Others, such as StorageTek's 9840/9940 and Quantum's DLT cartridges, will have labels and write protect switches with different colors to distinguish their WORM tape from their regular tape.
  • Tape protection added to the cartridge. On 9840/9940 cartridges, there's a distinctive impression on the cartridge that allows tape drive sensors to identify it as a WORM cartridge. On IBM's 3592 media, tamper-proof screws are used to prevent cartridges from being opened, and the tape film being moved and inserted into another cartridge.
  • WORM information written on the tape film at the factory. Every tape cartridge supporting WORM has information written to the tape film to indicate that it's a WORM tape.
  • Firmware upgrades for tape drives. While all current tape drives can read WORM cartridges, firmware upgrades are required to write and append to WORM cartridges. This firmware software is free and the upgrades can be done by technicians as part of normal maintenance.
Applications for WORM tape
There are risks associated with using WORM technology. To properly ascertain the risks, users need to consider both the applications WORM tape will support and how the data will be managed.

For example, most users expect a response time of five seconds or fewer to retrieve 60- to 90-day-old e-mails; if response times continually exceed 10 seconds, the help desk hears about it. For applications that require relatively fast retrieval, WORM tape's poor response times may be inappropriate. Joe Viviano at Bear Stearns and Co. discovered that WORM tape was a poor choice for their e-mail application because WORM tape couldn't deliver on users' expectations for timely e-mail message retrieval. The storage administrator switched to EMC's Centera disk-based WORM product for his company's e-mail because it provided quicker response times for archived e-mails.

How accurate are tape compression numbers? Tape manufacturers routinely advertise compressed tape capacities and transfer rates that double their stated native numbers. SDLT 600 media promises users 600GB of compressed capacity with a 72MB/sec transfer rate, while SAIT markets offer a 1.3TB compressed capacity and 78MB/sec transfer rate. How accurate are these projections?

Fuji Photo Film's national technical support manager, Mike McCorkle, finds that the only tape capacity numbers users can rely upon are the native capacity numbers. While users can expect increases in tape capacity with tape compression turned on, the amount of compression will vary by application.

So when vendors like Sony Electronics advertise a 2.6:1 compression rate for their AIT media and most other vendors claim compression rates of 2:1, users should not assume they will actually achieve these storage rates in their environments.

Also, numerous variables affect throughput speeds. While it is logical to expect that buying and deploying the latest tape drives and cartridges will decrease backup times, this will not necessarily be the case. Variables such as back hitches, network traffic, tape drive cache buffers, data block size, backup software, the number of tape drives and compression ratio will all play a role in determining the actual data transfer rate.

This was first published in July 2004

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