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Tape Library Speed

Shon Barrier
Occasional Advisor

Tape Library Speed

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
12 REPLIES
Alzhy
Honored Contributor

Re: Tape Library Speed

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!
Hakuna Matata.
Shon Barrier
Occasional Advisor

Re: Tape Library Speed

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

Re: Tape Library Speed

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..
Hakuna Matata.
Shon Barrier
Occasional Advisor

Re: Tape Library Speed

It is a DDS-3
Dave Dewar
Trusted Contributor

Re: Tape Library Speed

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
Occasional Advisor

Re: Tape Library Speed

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
Honored Contributor

Re: Tape Library Speed

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
Occasional Advisor

Re: Tape Library Speed

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
Trusted Contributor

Re: Tape Library Speed

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

Re: Tape Library Speed

Sounds as though you are using DDS2 tapes! The transfer rate on a DDS3 drive - anybody's - sith DDS2 tapes - sucks!
Don't fix what ain't broke!
Shon Barrier
Occasional Advisor

Re: Tape Library Speed

Definately, using HP DDS3 tapes
John Flint
Occasional Visitor

Re: Tape Library Speed

Shon,

Check to make sure your SCSI ID is not on ID 6. This ID is hard coded in Windows to support pluginplay devices. There is a lot of polling on that ID. You will notice quite a change in speeds if you change the ID. This solution was given to me by Veritas support.

John Flint