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Re: Overlapping backups: should I expect problems?
2008-09-16 04:49:34
Dustin J. Mitchell wrote:
On Mon, Sep 15, 2008 at 11:36 PM, John Morris <jman AT ablesky DOT com> wrote:
My question is, is this actually a good idea? Will there be any problems I
haven't anticipated, such as the two configs conflicting? For example, I
notice that there is only one /etc/amandates file that is presumably shared
by both configurations. I don't know whether the date to begin incrementals
from is from this file or from /var/lib/amanda/gnutar-lists.
No, it isn't a good idea, because there's a better solution that
doesn't involve this sort of gymnastics: RAIT. You can set up a RAIT
between the two tape devices, and then even if a drive is down, your
recoveries will work fine.
Dustin
The configuration I describe solves some problems that RAIT won't. See
if there's any error in my reasoning here.
The two configurations run on alternating days. One configuration runs
more often (3 days/week) on a smaller disk, so these backups only go
back a month. The other configuration runs less often (2 days/week) on
a larger disk, so these backups go back two months. With RAIT, you get
one configuration that stores identically replicated data, so there's no
opportunity to tweak one copy to go back further in time (is this true?).
Another relevant point is, the second disk was added for extra
capacity. With this extra capacity, we can run backups every single day
instead of only every two days. Thus, there is more granularity in the
backups with this configuration. If a user deletes a file accidentally
today, then we are guaranteed to have a copy less than 24 hours old.
For backups between 1 and 2 months ago, we don't care as much about the
granularity.
Whether or not the effort from this config's required gymnastics is
offset by these extra advantages, are there any other problems I can
anticipate? I'm no Amanda expert, so I fear not hearing the loud alarms
that would be set off in a more experienced user's mind when he hears
about this odd configuration.
Thanks for the quick response, Dustin. You're right that I may be a bit
over my head here. :)
John
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