Re: SVN MySQL Backend

In order to have a load balanced environment you need to have a back-end
filesystem which can cope with locking from multiple hosts.

NFS doesn't cut it which is why Kevin's environment uses SAN with veritas
cluster suite which performs SAN based locking properly.

The issue (I understand) is due to the use within apr_dbm to manage the
DAV activities database. This uses Berkeley DB which immediately makes it
unsuitable for NFS locking.

This also precludes you from being able to use NFS for storage with any
Apache MPM other than the prefork on UNIX systems (threads do *not* obey
POSIX locks properly) - see this thread on the dev@ list for details:
http://svn.haxx.se/dev/archive-2007-04/0288.shtml

I thought I had seen a reference in this thread to suggest that this might
be planned for 1.6.x but I may be mistaken.

I understand that there are various guys on this list performing
high-availability serving of repositories using SAN backends with
load-balanced front-ends.

Dg.

--
David Grierson
JPMorgan - IB Architecture - Source Code Management Consultant
GDP 228-5574 / DDI +44 141 228 5574 / Email david.x.grierson_at_jpmorgan.com
Alhambra House 6th floor, 45 Waterloo Street, Glasgow G2 6HS
 
Ruslan Sivak <russ_at_vshift.com> 
30/04/2008 15:33
To
kmradke_at_rockwellcollins.com
cc
users_at_subversion.tigris.org
Subject
Re: SVN MySQL Backend
kmradke_at_rockwellcollins.com wrote:
> Ruslan Sivak <russ_at_vshift.com> wrote on 04/29/2008 11:31:02 PM:
> 
>> I would like to have a load balanced SVN solution, but without shared 
>> storage.  It looks like MySQL can be set up in a cluster and be fault 
>> tolerant.
>> Did SVN ever get a MySQL backend?  Are there other solutions for 
>> load-balanced SVN Server?  I would rather not have to switch to SVK, as 
>> I'm used to all the SVN tools.
>> 
>
> Any reason you think you require load balancing? I/O is usually
> the bottleneck.  (We have maxed out our dual gigabit NICs a few
> times, but rarely are we CPU bound.)  We use veritas to provide
> hot-standby fail-over support.  Data is SAN, so we could have
> 5 9's there if we wanted.
>
> If you aren't adverse to spending some money, WanDisco would
> have some distributed solutions...
>
> 
Mostly for High Availability.  We are going to have two servers with 
what should be nice IO speeds, but no SAN.  If one of the servers is 
down for any reason, I don't want to lose data, and being able to commit 
to either of the servers would just be frosting. 
I think the proxy that was mentioned in 1.5 would work for us. 
Russ
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