Hot backups

[Rob Siemborski]

On Fri, 14 Nov 2003, Rob Siemborski wrote:

> On Fri, 14 Nov 2003, Simon Matter wrote:
>
> > IIRC taking a snapshot with LVM/XFS takes just a few seconds. I guess
> > everything should continue after the snapshot. What do the cyrus processes
> > do if they receive SIGSTOP? Will they stop immediately or will they not
> > stop at all? I mean, if a process receives SIGSTOP while it writes to a
> > file, will the write finish before the process stops?
>
> I'm pretty sure if you just stop the processes where they are, you'll
> still get an inconsistant store.  (E.g. the mail file is written out, but
> the index files aren't yet updated).

As I think about this further -- it might be possible to somehow signal to
all of the cyrus processes that they need to reach a quiescent state, but
I suspect that doing this to the point of absolute consistancy may be
significantly time consuming, as you may find yourself waiting for network
operations to complete also.

I don't think the work to even get to that point is trivial however.

-Rob

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Rob Siemborski * Andrew Systems Group * Cyert Hall 207 * 412-268-7456
Research Systems Programmer * /usr/contributed Gatekeeper