On Wed, 7 Apr 1999, Craig Murphy wrote:
[SNIP....]
We are doing AFS here, but a lot of the same principles apply...
// 1) I'm backing up 9GB of DFS data. Do I need 9GB+ for disk storage pool to
// backup (ie will migration keep up with backup)
Generally a good idea (according to the implementation people, and I tend
to agree) to have sufficient dasd to do your backups completely onto disk,
then migrate to tape. This is of course presuming that you can afford to
do so, otherwise, as much as you can afford is probably your best bet. I
have found in my case the migration to go considerably slower than the
backups when both are running, so if you can't do the hole backup onto
disk, make sure you start the migration early enough so that the disk
always has enough capacity to take on (largest file size) * (# of buta
sessions). Not doing this may cause deferred and/or missed files, and
will slow the process down due to the multiple retries ADSM will attempt.
// 2) Does anybody know for sure that multiple buta processes to disk will
// speed up backup
With my server (too small for what I'm trying to do, but you'll get the
idea) I found that up to 4 sessions was beneficial, but after that the
increase in overhead for each additional session actually slowed the
process as a whole. Your balance point may be higher or lower, but there
is bound to be one somewhere.
// 3) Anybody got any better ideas about backup up DFS families filesets that
// deosn't take as long as buta/butc.
I have tried the AFS back-by-file client, and found the overhead of
processing all of the virtualmountpoint's, plus the interaction you then
get with the AFS(/DFS?) client and cache makes it absurdly slow.
( <1.GB/hour)
-
Best regards,
Best regards,
Brian
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