Anyone whose ever had to rebuild a server just fromtapes might agree

[CLIFFORD ILKAY]

At 02:38 06/01/2004 -0500, John Macdonald wrote:
>On Mon, Jan 05, 2004 at 10:52:04PM -0500, cbbrowne-HInyCGIudOg at public.gmane.org wrote:
> > The only relatively "safe" way to get a quasi-atomic backup is to use
> > LVM, so that you can atomically "split off" a temporary copy of the
> > filessystem.  That makes the backup "atomic," which can allow satisfying
> > databases' needs for consistency.  You may need to recover the database,
> > but that usually fits into its design.
>
>With IBM's DB2 UDB database, there is an improvement
>to be made to this process.  It has a command to
>suspend write IO (which also updates the log before
>stopping writes).  Then you can split off a copy,
>and resume writes.  The copy can then be restarted (no
>recovery required).  Since it is only writes that are
>suspended, read transactions are not blocked at all,
>and write transactions can be carried out up to the
>point of committing (which then has to wait for the
>write resume).  Depending upon the mechanism used to
>split off the copy, this can be a very fast operation
>- using EMC Symmetrix storage array, I split off a
>copy of a 64 MB database with writes suspended for
>only a few seconds.

I take it this is/was a VC backed dot com:) That sounds like an awful lot 
of overkill just for a database that would fit on a Zip drive or a USB pen 
with room to spare. I presume you did not mean 64GB. It would not take much 
longer to shut the DBMS down, copy the files, and start it back up with 
PostgreSQL but then you would not have to do that anyway with pg_dump since 
pg_dump will make consistent backups of live data.

Regards,

Clifford Ilkay
Dinamis Corporation
3266 Yonge Street, Suite 1419
Toronto, Ontario
Canada M4N 3P6

Tel: 416-410-3326 

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