Lagging performanc on C1537A

[CA962745]

I purchased a used C1537A for use on my server. The drive seems to work fine (also passes LTT tests) except that it doesn't seem to backup faster than 52MB/min.

My configuration is a Novell NW5.0 server using BE8.0 on a 350MHz PII. The tape drive is on a separate card and channel from the HDDs and is currently on with the older SDT8000 (DDS-2) drive. The DDS-2 is able to backup at 40-48 MB/min.

I've already run TSATEST which shows an "Effective MB/min" of 100-150 MB going up to 400 MB/min in the second half of a 1.5GB test backup.

What could be the problem (if there is one)? And how do I resolve it.

Thanks in advance.

[Eugeny Brychkov]

Boaz,
if special perfomance testing programs show good perfomance but actual backup does not then usually problem is in backup application's data block size. Check it and try increasing and look to perfomance change
Eugeny

[CA962745]

I already tried 32K block size (52MB/min) and 512 byte size (49MB/min). So I'm not sure that this is the problem.

Note: The HP LTT software says that the drive needs cleaning, but I've already run the tape cleaner through about 7 times. Should I run it through some more or should I try to recalibrate the heads?

Boaz

[Lewis Finch]

Your message indicates you have the drive piggybacked to a DDS 2. Here are a couple of things to try. Remove the DDS2 so you only have the DDS 3 on the Bus. disable wide negotiation in the SCSI BIOS. Drop transfer rate to 10. Set software block size at 2k.

[CA962745]

I dropped the block size to 2K, disabled wide support and set speed to 10. The drive still seems to be running at the same speed (I didn't run the identical job) and shoe-shines about every 4 minutes.

the one thing I noticed was that when the software was backing up large text-based files (like one of my databases) that are likely highly compressible the speeds will jump from about 750KB/s to 1.5 to 3MB/s.

I tried setting up another machine with Win2K to test the drive out using an Adaptec AHA-1535 (154x) adapter. It read the drive information data OK, but it gave a "I/O request was refused by the OS" error whenever I ran a connectivity test or any read/write tests.

Any other suggestions?

Boaz

[Eugeny Brychkov]

Did you check this?
http://www.hp.com/cposupport/information_storage/support_doc/lpg50063.html
Eugeny

[CA962745]

Yes.

When I'm working on the server I'm running on an AHA-2940U2W. The drive came with the AHA-1535 and the LTT software can read the data from the tape when using this card. It's the OS that is blocking a "Write buffer" request.

Boaz

[CA962745]

I just ran a full backup for the first time as a test on this machine. I kicked the tape out after saving only 9.5 GB. I got the feeling that the compression wasn't working well because most of the files being backed up were graphics files, many of which are already compressed.

So I ran a backup after having truned off all compression and the backup speed went up to 57.7 MB/min for the original backup job that was originally only seeing a throughput of 52 MB/min.

I guess that's the best I can expect unless others have another suggestion.

BTW, would I see better performance with more recent hardware versions of the DAT24 drive?

Boaz

[CA964019]

I have the same issue, only I'm on a Windows 2000 server using Backup Exec 9.0. Backup Exec show my speed at around 52 mb/min. I'm using brand new DDS3 tapes and am using an Adaptec 2940UW SCSI card. Everything has been updated to the latest firmware. Any ideas on this one???

[CA843380]

Hi,

There is a set of performance checking tools on the hp support web site for DDS and Ultrium products. These allow you to check the speed of your target disk subsystem, and check the speed of transfers from memeory to tape and also check transfer rates for different compression ratios. Try:

http://h20000.www2.hp.com/bizsupport/TechSupport/DriverDownload.jsp?pnameOID=12183&locale=en_US&taskId=135&prodTypeId=12169&prodSeriesId=42846#Microsoft Windows 2000

and select your OS. Scroll down the table and look for PAT, HPcreatedata, HPreaddata and HPtapePerf.

Cheers,

Dave Dewar.