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[Networker] Bootstraps during Staging
2005-09-01 12:00:41
On 1 Sep 2005, at 15:36, Davina Treiber wrote:
I think that the media database should be backed up to tape after the
savesets have moved from disk to tape, but before they are deleted
from their source device.
Or am I missing something?
No you're not missing anything, but there are very many instances
when the media database on disk is newer than the backup of it on
tape. Running any backup that doesn't include the bootstrap will
create this situation, and any time that a backup is in progress
the same could be said. So what is the solution? The only way you
could get round this is to backup the bootstrap more often. There
is nothing at all to prevent you doing this. I don't think most
people would see this as a problem, but it all depends on your
level of paranoia.
My suspicion is that the staging code is a part of Networker that's
not as well-exercised as some others, and therefore some of the
implications might not have been worked through. You're
right that the media database isn't committed to tape until the
bootstraps go out at the end of
a group, but I think most people would accept that `in progress'
backups are a special case. My worry with staging is that you could
lose track of a backup which was done some time ago, and on which
subsequent incrementals rely. In a largeish silo scanning all the
tapes to find a specified saveset would be distinctly slow. Staging
is one of the rare circumstances in which perfectly good, non-expired
savesets are deleted. I can't think of another scenario in which a
saveset which predates the most recent group completion would get
lost in this way, and I can't see how I could intervene to save the
bootstrap at the right point.
ian
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