Tape Performance on 3580
Hi guys, this is actually not a TSM question but one for the hardware gurus. We are running a backup under AIX using the savevg command and Ultrium 3580 tape drives. With topas I can see a data transfer rate of about 1MB/sec. We attached the drives via Fibre Channel and a SAN Data Gateway. The blocksize of the drive was set to 2048 (since one of the SAN guys told me FC transfers with a blocksize of 2048). I started savevg with "-b4" meaning to write 4x512Byte blocks (=2048). With the mentioned speed the drives are seriously crawling. Am I missing out something here? Any clues?? Thanks Lars
Re: Tape Performance on 3580
Lars Bebensee wrote: >Hi guys, > >this is actually not a TSM question but one for the hardware gurus. We are >running a backup under AIX using the savevg command and Ultrium 3580 tape >drives. With topas I can see a data transfer rate of about 1MB/sec. We >attached the drives via Fibre Channel and a SAN Data Gateway. The blocksize >of the drive was set to 2048 (since one of the SAN guys told me FC >transfers with a blocksize of 2048). I started savevg with "-b4" meaning to >write 4x512Byte blocks (=2048). With the mentioned speed the drives are >seriously crawling. Am I missing out something here? Any clues?? > >Thanks > >Lars > > Hi, I think your problem is you are not feeding the data to the tape drive fast enough for it to stream, therefore it is stopping waiting for data and then starts when it gets some. The stop and starts kill the performance. I would try increasing two different values: chdev -l sys0 -a maxbuf=100 savevg -b200 . This should improve the streaming of data to the tape drive. You may have to play with these numbers some to get the optimal performance. Good Luck and let us know how you did. -- Regards, Mark D. Rodriguez President MDR Consulting, Inc. === MDR Consulting The very best in Technical Training and Consulting. IBM Advanced Business Partner SAIR Linux and GNU Authorized Center for Education IBM Certified Advanced Technical Expert, CATE AIX Support and Performance Tuning, RS6000 SP, TSM/ADSM and Linux Red Hat Certified Engineer, RHCE ===
Re: Tape Performance on 3580
Just a guess -- but I'd ignore the FC transfer size and use a device blocksize of 128K or 256K (can't remember off the top of my head what LTO uses as a maximum). The FC transport layer should split/reassemble the blocks with no problem. For example, our SAP database is FC attached and Oracle is configured to use an 8K blocksize for all disk I/O -- and that's been working for several years now. Tom Kauffman NIBCO, Inc > -Original Message- > From: Lars Bebensee [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, August 13, 2002 9:24 AM > To: [EMAIL PROTECTED] > Subject: Tape Performance on 3580 > > > Hi guys, > > this is actually not a TSM question but one for the hardware > gurus. We are > running a backup under AIX using the savevg command and > Ultrium 3580 tape > drives. With topas I can see a data transfer rate of about 1MB/sec. We > attached the drives via Fibre Channel and a SAN Data Gateway. > The blocksize > of the drive was set to 2048 (since one of the SAN guys told me FC > transfers with a blocksize of 2048). I started savevg with > "-b4" meaning to > write 4x512Byte blocks (=2048). With the mentioned speed the > drives are > seriously crawling. Am I missing out something here? Any clues?? > > Thanks > > Lars >
Re: Tape Performance on 3580
LTO drives will "crawl" unless they are streamed.
The LTO blocksize should be set as high as possible, 256KB is not to
large.
If your disk and application cannot write at 15 MB/sec, the best you can
expect is a few MB/sec. There is no in-between.
Orville L. Lantto
Datatrend Technologies, Inc. (http://www.datatrend.com)
IBM Premier Business Partner
121 Cheshire Lane, Suite 700
Minnetonka, MN 55305
Email: [EMAIL PROTECTED]
Lars Bebensee <[EMAIL PROTECTED]>
Sent by: "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]>
08/13/02 09:24 AM
Please respond to "ADSM: Dist Stor Manager"
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Subject:Tape Performance on 3580
Hi guys,
this is actually not a TSM question but one for the hardware gurus. We are
running a backup under AIX using the savevg command and Ultrium 3580 tape
drives. With topas I can see a data transfer rate of about 1MB/sec. We
attached the drives via Fibre Channel and a SAN Data Gateway. The
blocksize
of the drive was set to 2048 (since one of the SAN guys told me FC
transfers with a blocksize of 2048). I started savevg with "-b4" meaning
to
write 4x512Byte blocks (=2048). With the mentioned speed the drives are
seriously crawling. Am I missing out something here? Any clues??
Thanks
Lars
Re: Tape Performance on 3580
While your co-worker is correct that the Fibre Channel payload is approximately 2k, the logical leap that you would want to match your blocksize to the Fibre channel payload size is completely erroneous. Having a blocksize of 2k as opposed to 256k induces a 128 fold increase in the communication overhead. I.E. for every 256KB of data you are going through the protocol overhead 128 more times. It's like buying groceries, but instead of filling up your cart and taking it to the checkout cashier, you get 1 item at a time and bring it to the cashier. But you not only bring 1 item at a time, but you pay for each item individually. The checkout cashier's bar code reader can only handle one item at a time, so you might as well get one item at a time. The tape drive and the fibre channel protocol both perform significantly better at 256KB blocksizes. James Thompson _ Chat with friends online, try MSN Messenger: http://messenger.msn.com
