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Re: Berkeley is good stuff!

From: Soren 'Frank' Munch <sm_sbv_at_u5.com>
Date: 2005-07-02 03:33:23 CEST

Ryan Schmidt wrote :
> I was under the impression that a hot-backup is only necessary for
> BDB repositories -- that FSFS repositories can simply be copied using
> a normal operating system copy. In other words, the existence of hot-
> copy for BDB is not a benefit of BDB; the necessity of using hot-copy
> for BDB is a drawback of BDB. At least that's what the list has led
> me to believe.

But also repos running on Berkeley can be backed up with a normal operations
like cp -Rfp or tar. The tricky question is how long we need to take the
svn-service down, to ensure that data written to the repos during the backup
doesn't screw up the integrity of the files.

I think it is like this:

1. fsfs without using snapshot file system (or bdb by simple copying): We must
ensure that no write operations takes place while we back up the files. This
means closing the svn service, copying the files and when completed, opening
svn again. This is the method we currently use. If the repo is very large
this means some downtime.

2. fsfs using a snapshot-able file system: Closing server, taking snapshot,
opening. In other words the snapshot functionality allows us to close for a
very short time but close we still have to, we can't risk snapshotting in the
middle of an operation.

3. BDB, using snapshot - I'd imagine that this was similar to 2. Or is there
even some mechanism in svn+hotbackup that can ensure data integrity without
stopping the svn-server at all, even in the middle of an operation? As there
is already 'atomicity' built into svn this could be the case. If so this
would be a real asset for busy svn system.

Somebody must know about this... :-)

Soren 'Frank'

On Saturday 02 July 2005 06:56, Ryan Schmidt wrote:
> On 02.07.2005, at 01:17, Soren 'Frank' Munch wrote:
> > On Saturday 02 July 2005 04:42, Christopher Kreager wrote:
> >> We chose the Berkeley path with the intention to use the
> >> hotbackup, which
> >> helps for running two db back to back for recovery with less down
> >> time. At
> >> the moment SVNADMIN can not seem to handle loading the dump file
> >> of this
> >> size when restoring to BDB, but works just fine going to FSFS.
> >
> > FreeBSD 5.x/6.x has a filesystem snapshot-option. It can most
> > probably be
> > used to get "hotbackups" with fsfs. I don't know if Linux/OS X has
> > something
> > similar.

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Received on Sat Jul 2 03:39:11 2005

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