Monday Feb 07, 2011

No Red Tape Here, Part I.

Old Tape DriveSome of us remember the good old days of computer tape. For example, I remember that the write protect ring on the back of the 6250 tape reels had a perfect balance: grasping the little tab and flinging it at the wall, the ring bounced back to be caught without leaving a mark on the lab. We did this as we waited for long compiles to finish and found other creative amusements with this simple component; I am old enough to escape retribution from my supervisors in making this admission, as they are long retired. But, I digress.

Tape as a backup medium – although in a much more sophisticated form – remains a staple of large enterprise backup. Last week we had a big announcement of Oracle's StorageTek T1000C Tape Drive, which offers 5 TB native uncompressed storage and a data transfer rated at nearly ΒΌ gigabyte per second. (To keep things in perspective, the 6250 stored 140 MB; I don't remember how slow it was, but it was well under 1 megabyte per second...) As a result of this announcement, we have released a number of technical papers that I thought I would discuss in a couple of blogs.

First of all, in thinking about speed, you won't want to miss Evaluating Tape Drive Performance White Paper, by Oracle engineer Dwayne Edling. Dwayne opens the paper by discussing the three components that limit tape speed:

  1. The speed that the storage application sends data to, or processes data from, the drive.
  2. The speed of the host interface between the drive and the application.
  3. The speed that the tape drive writes or reads data at the head/media interface.

6250 TapeHe then goes on to test the T1000C Tape Drive under a variety of conditions and comes to the important conclusion that in most situations, either the storage applications' speed or the drive throughput speed are the limiting factors in tape drive performance. Typical storage application throughput of 50-60 MB/s falls far short of the 400 MB/s maximum speed of a 4GB SCSI FCP interface. Even with compressed data, current tape drive technologies are also not able to write or read data any faster than a 4 GB (400 MB/s) SCSI FCP interface can push the data.

Back in the Jurassic age of computing, we naively assumed that tape storage was essentially "forever." That proved not to be the case! Another very interesting paper that addresses the issue of longtime archival is Protecting Your Archival Data With Improved Tape Dimensional Stability. This brief paper gives you some insight into the factors that make for longer lasting tape – its dimensional stability. Of course, some of these are environmental, but the substrate used is very important; advances in tape substrates have resulted in significant improvements over the last decade. Oracle's selection of aramid as the StorageTek T10000 T2 substrate has resulted in superior tape dimensional stability performance and long-term archival life.

Finally, don't miss Redefining Tape Usage With StorageTek Tape Tiering Accelerator and StorageTek In-Drive Reclaim Accelerator.The StorageTek In-drive Reclaim Accelerator and StorageTek Tape Tiering Accelerator, an important innovation in the T1000C Tape Drive, provide the capability to randomly access, add or delete physical partitions. This paper goes into the nitty gritty of how this works.

Existing tape media can store more than a terabyte of user data. In the near future, a single tape media will hold tens of terabytes, with 100 TB capacities in the foreseeable future. Managing these multi-terabyte tape cartridges requires a new approach for managing data on tape. Oracle has developed a new tape storage format with the StorageTek T10000C tape drive, using an innovative partitioning architecture, that allows the addition or removal of storage space as needed. With these capacities and efficiencies, tape remains an important medium for enterprise archiving.

- Kemer


Rick Ramsey
Kemer Thomson
and members of the OTN community


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