ADSM-L

Re: Restore on NT server

1999-01-28 11:04:40
Subject: Re: Restore on NT server
From: "Kelly J. Lipp" <lipp AT STORSOL DOT COM>
Date: Thu, 28 Jan 1999 09:04:40 -0700
Depending on how the 100 GB is laid out on the server, you can see restore
rates of around 20 GB/hour.  We did some testing in a site similar to the
one you describe.  The data on the client existed on multiple disks (or
partitions) so were able to use multiple restore processes.  Our client was
a Netfinity box, PII 350 with 128 MB and three disks.  So we started three
restore processes from the AIX ADSM server.  The data was on 3570 tape in a
robot.  Our maximum restore rate was 18 GB/hour in this setup with the
three processes.  The CPU utilization on the client averaged 80%.  We
probably could have squeezed another process in and gotten over 20 GB/hour,
but we didn't have another disk on the client.

If you are going to set up restores this way, you must optimize your backup
as well.  It wouldn't do to have all of client disks data on one tape, for
instance.  In our test, the data appeared to be on two tapes and the server
shared these tapes with the three restores.  We were seeing "waiting for
off-line media" messages on each of the restore clients.  However, the
waiting times were very short.  Perhaps someone is ADSM land can confirm
that we could have seen a "sharing" of these tapes.

Bottom line: be smart in what you're doing and you can get great restore
rates.  We've seen a lot of sites with a small C partition for the OS, and
a giant D partition with everything else.  Easy to manage, but a bear to
restore fast.  I'm not suggesting eliminating the underlying RAID array,
but perhaps partition it at the OS level so you can bring more backup and
restore streams to bear on the problem.

BTW, we were able to achieve 20 GB/hour backup times as well using up to
four backup streams.  Again, our configuration allowed this since we had
more than four partitions.

Kelly J. Lipp
Storage Solutions Specialists, Inc.
www.storsol.com
lipp AT storsol DOT com
(719)531-5926

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