Re: Shared storage for subversion repository

Hi Ryan,

Basically it comes down to this thread on the developers list:
http://svn.haxx.se/dev/archive-2007-04/0288.shtml

The key point here is that apr-util still uses DBM files:

"mod_dav_svn maintains an activity database - a mapping of DAV-generated
identifiers to Subversion transaction id's. It implements this using
APR-util's dbm implementation, which may be BDB, gdbm, or one of several
other dbm-a-like implementations."

Locking files held on NFS servers *should* work if the lock manager
implements locks properly - my personal experience of this has been mixed
at best.

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
 
Ryan Schmidt <subversion-2008c_at_ryandesign.com> 
22/09/2008 19:29
To
david.x.grierson_at_jpmorgan.com
cc
Murli Varadachari <mvaradachari_at_facebook.com>, 
"users_at_subversion.tigris.org" <users_at_subversion.tigris.org>
Subject
Re: Shared storage for subversion repository
On Sep 22, 2008, at 9:59 AM, david.x.grierson_at_jpmorgan.com wrote:
> On Sep 22, 2008, at 9:27 AM, Murli Varadachari wrote:
>
>> I am testing out an arrangement whereby the subversion repository 
>> is located on shared partition [ netapps partition ] -- and 
>> accessed by multiple subversion hosts via NFS. My plan is to have 
>> one of these hosts be used for read-write access and the rest for 
>> read-only access. I have tested this out and it looks O.K so far.
>>
>> Q: Can this arrangement be used to have all hosts be capable of 
>> read-write access. Can subversion handle multiple access points on 
>> the same repository.
>>
>> Cheers
>> Murli
>>
>> P.S: I am using FSFS
>
> No - this will not work with NFS access from multiple hosts.
>
> NFS (even with correctly working locking) does not work with 
> Subversion
> 1.5 or lower because the underlying apr libraries used for 
> transactions
> still use DBM files - which require working locks.
>
> You will eventually end up with repository corruption - particularly
> likely when large commits are performed.
David,
The FAQ says this is OK; do you have information to the contrary?
http://subversion.tigris.org/faq.html#nfs
It warns against storing a BDB repository on NFS, but says "If you 
are using the FSFS repository back end, then storing the repository 
on a modern NFS server (i.e., one that supports locking) should be 
fine." And Murli did say they are using FSFS.
Murli,
You may want to look into svnsync, available with Subversion 1.4 and 
up. It can be used to create any number of read-only mirrors of your 
main repository. Each mirror would have its own local copy of the 
repository.
You can even set up a write-through proxy so that people can check 
out from the read-only mirrors and when they check in it will be 
redirected to the master. This is available in Subversion 1.5 and up.
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