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тАО06-29-2009 06:06 AM
тАО06-29-2009 06:06 AM
BACKUP/IO_LOAD - What Value
I'm running a fast EVA8000 on a quiet ES45. Any recommendations?
Rob.
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тАО06-29-2009 07:18 AM
тАО06-29-2009 07:18 AM
Re: BACKUP/IO_LOAD - What Value
http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1143614
More is not necessarily better as far as a storage controller is concerned, and the general recommendation of the fellow that implemented this knob (Guy Peleg) has classically been eight; the default. But you can try a few other values and see.
Do recognize that various newer storage controllers might not appreciate the blizzard of I/O that classic I/O on OpenVMS can generate; some newer widgets react, um, poorly to I/O overloads. I'm comparatively cautious around pushing most any FC SAN storage controller from most any vendor harder.
I prefer to treat /IO_LOAD as a governor, and not as an accelerator.
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тАО06-29-2009 12:50 PM
тАО06-29-2009 12:50 PM
Re: BACKUP/IO_LOAD - What Value
If less use a larger IO_LOAD value and if too large use a smaller value.
(*) If the disk presented is a RAID set then use 2-3 times number of disks in this RAID set.
No need to shove more down the throat of a disk drive than it can swallow at a time.
/Guenter
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тАО06-29-2009 01:38 PM
тАО06-29-2009 01:38 PM
Re: BACKUP/IO_LOAD - What Value
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тАО06-30-2009 02:54 AM
тАО06-30-2009 02:54 AM
Re: BACKUP/IO_LOAD - What Value
If the default's 8, I'd probably be looking at that and then determining what else goes on and what other things are affected by me changing the value of the qualifier (i.e. don't just look at the backup, look at the effect it has on everything around it).
Steve
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тАО06-30-2009 03:05 AM
тАО06-30-2009 03:05 AM
Re: BACKUP/IO_LOAD - What Value
My EVA is practically idle most of the time, so if there's a way of pushing it harder and getting the transfer speeds up, then I'd like to pursue it.
Rob.
BTW - How are things down there?
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тАО06-30-2009 06:13 AM
тАО06-30-2009 06:13 AM
Re: BACKUP/IO_LOAD - What Value
I then tried increasing various UAF parameters, but again, it had no effect.
Think I'll just live with what I always knew - VMS is very poor at feeding fast tape drives!
Thanks for your responses. Maybe one day BACKUP will be less of a black art.
Rob.
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тАО06-30-2009 09:23 AM
тАО06-30-2009 09:23 AM
Re: BACKUP/IO_LOAD - What Value
What's the LTO4 hooked to?
If hauling the blocks off disk and up into the host and back out to the controller is in order (and this and file fragmentation and such is particularly important when looking to keep a fast tape busy), then BACKUP is sensitive to the proportions among the process quotas. See:
http://labs.hoffmanlabs.com/node/49
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тАО06-30-2009 10:40 AM
тАО06-30-2009 10:40 AM
Re: BACKUP/IO_LOAD - What Value
You can set /GROUP=0. /CRC is a big hog of CPU. With todays tape and Fibre Channel technology I don't know what benefit using /CRC still provides. From my faulty memory, the undetected error rate is about 10E-34 and CRC just increases that to 10E-51. When you crunch the numbers, you would have to be backing up a very, very long time to get an undetected error with out using CRC.
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тАО06-30-2009 10:55 AM
тАО06-30-2009 10:55 AM
Re: BACKUP/IO_LOAD - What Value
With BACKUP performance one basic test _ ALWAYS - is doing the same backup to the null device: $ BACK disk: NLA0:dummy.
This gives a good idea about how fast files can be copied from the input disk.
One parameter which I found sensitive in my testing was WSQUOTA. Smaller values - YEAH - give better performance (less than 50,000 pagelets).
Ah, and just for fun try a BACKUP/PHYSICAL of that disk device to tape. That takes the file system overhead out of the loop.
/Guenther