Tape Library Speed

[Shon Barrier]

I have a C1157A attached to an Adaptec 2940 SCSI card. I am consistenly only getting 22MB per minute of speed during my backups.

According to the specs of Adaptec's web site, I should be getting up to 40MB per second.

Anyone have any ideas as to why my backup times are so slow? It is not a high end server (it has WD 7200rpm drives) but I feel that I should be getting much faster backup speeds.

Thanks,

Shon

[Alzhy]

If a C1157A is a DDS3/4 tape-drive )or even a SDLT).. be happy with the 22MB/sec unless it is a typo that you claimed you are only getting 22MB per MINUTE!

[Shon Barrier]

No, I'm only getting 22MB per minute. It is taking about 6 hours and 40 minutes to backup 9.2 GB.

[Alzhy]

What is the C1157A? A DDS1 or DDS2 drive? If they are.. then that's close to spec. On UNIX , my DDS1/DDS2 drives averages about 500-600 Kb/sec..

[Shon Barrier]

It is a DDS-3

[Dave Dewar]

Hi Shon,

What cartridge are you using for your DDS3 drive? I also cannot find any record of a C1157A product number? is this a HP DDS3 product?

If it is a HP DDS3 drive then the sustained native performance is 1MB/s in DDS3 mode and 500KB/s in DDS1/2 mode.

Please do not confuse the SCSI HBA 2940 burst date rate specification with the sustained write/read performance of the tape drive. 40MB/sec is the maximum speed that your 2940 can go, and you will only see this performance during actual SCSI data transfer. The system performance will be limited by the slowest item on your bus, probably the tape drive.

Also, with a typical user file system and a typical level of fragmentation, I would not expect you to acheive any more than 5-10MB/sec from your WD 7200rpm disk drives, unless you are performing some sort of image backup and accessing the disk drive in sequential mode.

Cheers,

Dave Dewar

[Shon Barrier]

Sorry, it is a C1557A. Any ideas on how I can increase the performance? 22MB per minute is significantly less than 5-10MB per second.

Thanks,

Shon

[Scott McIntosh_2]

C1157A? Don't know what one of those is. What is it?

22MB/min? How are you measuring this? What are you using to run the tape backup?

2940 is a fast-wide card, 20MB/s. 2940UW is an ultra-wide card, 40MB/s. I don't think the 2940 came in a non-wide version. So exactly which 2940 do you have?

Bottleneck could be the reading of the disk or the writing of the tape. It's Windows. What do you do to monitor I/O throughput on a per device basis on Windows? No Glance on Windows.

Thanks,
Scott
HP Support

[Shon Barrier]

The backup software that I'm using is giving me the data transfer rate. Also, I've verified this by the amount of data being backed up versus the amount of time that it is taking.

Shon

[Dave Dewar]

Shon,

Ok, you have a DDS3 tape autoloader.
You are not going to be able to go faster than the slowest item in your SCSI IO subsystem. On specs the slowest item is your tape library.

The sustained transfer rate of the C1557A is 1MB/s using DDS3 tapes and 510KB/s using DDS1 and DDS2 tapes, if you have hardware compression enabled and have a decent compression ratio on your data, expect this to double, but that will depend on how compressible your data is.

Its possible that your WD 7200 (IDE) drives have heavy fragmentation, and/or small files and this could limit you below the tape drive levels.

We have an excellent trouble shooting guide at the following link and are Library and Tape Tools software has performance tests that allow you to verify memory to tape drive and disk to memory performance to identify bottlenecks as well as doing many other things.

Performance guide
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50460&locale=en_US

LTT ( choose your OS)
Links for LTT and other performance tools at end of performance guide above

Cheers,

Dave Dewar