Subject: generation of backup volumes
From: [EMAIL PROTECTED]
Date: Fri, 14 Jan 1994 09:53:10 -0500 (EST)
We need more control over our generation of backup volumes than the
'vos backupsys' command provides (even with the new -exclude option).
One option is to create a script which uses some algorithm to generate
a list of volumes to be cloned and then invokes the 'vos backup' command
for each one.
Is there any significant loss of efficiency in using 'vos backup' rather
than 'vos backupsys'?
I would appreciate it if sites which currently use such scripts would
email me a copy.
At MIT, we do a vos backup of about 20,000 volumes nightly. It turns
out that "vos backupsys" takes too long, as does just about every other
method. The only way that we can complete this task in about 7 hours
is:
- Have a list of the servers, and split them equally among four threads
of the program, running in parallel. Each thread will then do a
"vos listvol" on the server, and then "vos backup" of each appropriate
volume that needs to be cloned nightly (after checking the name of
the volume).
It turns out that a "vos listvldb" is too expensive, and too slow, and
that this out-performs "vos backupsys", even if you were only to specify
a server. Somehow, there is an additional advantage gained by
completing all the transactions on a single server before moving on to
the next; I can only attribute this speedup to the inefficiencies of the
kernel in establishing a connection to a new host. RX is based on UDP,
so theoretically, this speedup should not be occurring, but it is.
-Richard Basch
MIT IS/Athena Development
