fP and data integrity...how to maintain on non-quiescent systems?

[Bill Campbell]

On Mon, Feb 19, 2007, Kenneth Brody wrote:
>Quoting Bill Campbell (Sat, 17 Feb 2007 19:11:20 -0800):
>[... Backing up an active database ...]
>> MySQL handles this by (a) making a snapshot of the database, and noting
>> the offset within the current logfile.  The secondary system is created
>> from that snapshot, then it's given the offset in the remote log file,
>> effectively does a seek into that file, and proceeds to continuously
>> update its databases, keeping track of its current position in the log
>> processing.
>[...]
>
>How does MySQL handle updates while taking the snapshot?  How long
>does it take to make the snapshot on such a large set of tables?

It doesn't.  Their recommendation on the inital snapshot is to (a) stop the
mysql server, (b) make a tarball or other binary backup of the related
database(s), (c) record the name and offset of the binary log file, and (d)
restart mysql.

It took me a bit of documentation reading to figure out how to do this when
I set it up the first time (and will again if I ever have to do it again
as I haven't done it enough times to commit it to memory :-)

I've also seen presentations on the Veritas file systems where they claim
to be able to freeze a file system for backup while maintaining
transactions separately which will then be played back into the file system
when its unfrozen.  I've never had to deal with major enterprise sized
systems that require 24x7x365 update, dealing with SMB systems where it's
possible to take them down for this type of activity.

Bill
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