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RE: <?> Deltify, huh, what is it good for<?> Questions on Deltify and recovery

From: Peter Kahn <pkahn_at_connected.com>
Date: 2004-12-14 14:38:53 CET

I actually saw a bit of a difference between the time it takes to
perform a recovery before and after a deltify, but I cannot be sure
because I lack a fool proof method of introducing corruption into my

I have a repository that is 5.5 GB with about 2 GB of that as unused DB
log files. Recovery for me takes about 16 hours. Here are my stats:

        Linux 2.4.20-8
        2.6 GHz Processor
        1 GB Ram
        Stripped and Mirror disk

Svn 1.1.1 (r11581)
Berkeley DB 4.2.52


I really just want to find a means of limiting my downtime. We have
begun to banter around the idea of running two repositories where one is
essentially a mirror served by a second instance of svnserve and a hook
script ferries transactions across. Should we have a crash that
corrupts the database, the primary would be moved out and the secondary
would become the primary. This would mean all users would need to do
the switch command with the repository setting.

How do people deal with this problem, are they using hotcopy after each
transaction? Or some other means to allow a roll back prior to the
corruption or is 16 hours an unusually long time for a recovery.

In addition, I find the lack of any useful statistics when recovery is
needed to be a real problem. I cannot gage how long the press will take
and I cannot tell what it might be doing.

-----Original Message-----
From: kfogel@newton.ch.collab.net [mailto:kfogel@newton.ch.collab.net]
On Behalf Of kfogel@collab.net
Sent: Monday, December 13, 2004 11:51 AM
To: Peter Kahn
Cc: users@subversion.tigris.org
Subject: Re: <?> Deltify, huh, what is it good for<?> Questions on
Deltify and recovery

"Peter Kahn" <pkahn@connected.com> writes:
> Here is the real question. I have read some posts on other lists
> how running deltify can be a useful maintenance operation. I have
> the description of what deltify does to be a little Spartan for my
> tastes and I'm just not sure if it would procude any kind of gain.
> If I run deltify on a daily basis, would it make a recovery faster?
> I should be running deltify regularily, should it be run just on HEAD
> should it be run on ALL revisions since the last time deltify was run?

Unfortunately, 'svnadmin deltify' is not useful these days (it's
basically a no-op), and won't make recoveries faster.

In the dev@ list, we're discussing steps we can take to make
Subversion's interactions with Berkeley DB more stable (I hasten to
point out that the problems appear to be with Subversion's usage of
BDB, not with BDB itself). We're getting a lot of help from the folks
at Sleepycat.com. See this thread


for more.


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Received on Tue Dec 14 14:39:51 2004

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