On Tue, Aug 31, 2004 at 04:29:43PM -0400, Joe Konecny wrote:
> To me that's ideal since the data collection
> in our factory runs 24-7.  Even on Sat and Sun when I'm not
> there the tape is still over written with the latest data.
> If Amanda does only copies the data to a holding area and
> we lose a drive on Sunday night I have massive problems.

Consider your current Arcserve scheme.  If you lose the
data-collection drive during a weekend backup run, your recent
data is toast.  The only backup since Thursday night has been
destroyed (partially overwritten) along with the live data.  Low
probability, but it could happen.

Now consider what we're suggesting -- Amanda backing up to
holding disk, and the backups being flushed to tape on Monday.
To lose the data, you'd have to lose both the live-data disk
*and* the holding disk, although the restriction that it has to
happen during a backup run doesn't apply.

Losing a disk at some point over the weekend is a higher
probability than losing it during the backup window, but losing
both of them at once is *much less* likely ...  unless there's a
fire in the machine room or similar catastrophe over the weekend,
in which case your current tape backup, which was still in the
drive, is toast too -- under either scheme -- and again your most
recent backup is the one from Thursday night.

> That's what I call a disaster and I don't see how amanda
> can help me there.

Amanda is approximately as able to help there as your current
scheme (equal, or a little better, but unless I'm missing
something, not a lot better -- the improvement is precisely the
difference in probability of data loss between the two schemes.)
Amanda can also guard against failure modes that your current
scheme doesn't guard against -- or, as I've described, it can be
configured not to guard against them, if that better suits your
requirements.

--

|  | /\
|-_|/  >   Eric Siegerman, Toronto, Ont.        erics AT telepres DOT com
|  |  /
It must be said that they would have sounded better if the singer
wouldn't throw his fellow band members to the ground and toss the
drum kit around during songs.
        - Patrick Lenneau