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Re: FSFS performance on NAS/NFS

From: Justin Johnson <justinjohnson_at_gmail.com>
Date: 2007-03-09 16:51:35 CET

On 3/8/07, C. Michael Pilato <cmpilato@collab.net> wrote:
> > CollabNet said there wouldn't be any data integrity issues with
> > NAS/NFS and FSFS as long as only one server was accessing the
> > repository and the version of NFS supported locking. Mounting on
> > multiple servers concurrently and load balancing would require a
> > clustered file system.
> >
> > My question was specifically related to performance though. Is there
> > anyone out there using FSFS repositories on NAS/NFS? Does the
> > performance "really really really suck?" Should I go with Berkeley
> > instead?
> [I'm not subscribed to users@, just got pointed to this thread by a
> colleague, so if your response is aimed at me, please explicitly Cc me]
> Justin, it's possible that I was actually one of the folks from CollabNet
> that you spoke with. Allow me to make some clarifications.

Yes, you are the one I spoke with.

> First, it is true that CollabNet uses BDB for its repositories. The reasons
> for this including the following:
> * We've been hosting Subversion repositories for much longer than FSFS
> has even existed.

It occurred to me that this might be a factor in why you use BDB.

> * Our customers pay us to make sure they have Subversion access with
> glorious uptime, and frankly don't care how we give it to them as
> long as they aren't missing out on features or paying some notable
> performance penalty. If anyone stands to complain about our choice
> of a back-end, its our own Corporate Operations team that have to
> deal with the backlash when a site outage occurs. And as recently
> as a couple of weeks ago when I last posed the question, CollabNet's
> Ops group is quite happy with BDB.

This is good to know.

> * Our Ops group tells me that our particular backup strategies (which
> are a critical piece of CollabNet's hosted offering) would actually
> be more complicated and much slower with FSFS versus BDB.

Also good to know. Currently we're just doing incremental dumps of
FSFS every half hour and full dumps weekly. I'll have to become more
familiar with the way it works for BDB.

> Secondly, it is true that CollabNet often hosts its repositories on NFS.
> But we're not in a position to make general claims about Subversion
> repositories hosted on network shares. We have tested and validated our
> specific deployment scenario, which involves the use of a specific operating
> system, a specific kernel for that OS, a NetApp NAS device with specific
> configurations, and so on. Further, our repositories are never accessed
> from multiple NAS client machines. So, we can say the following:
> * we feel pretty good about how things work for us, and,
> * in theory, there's no reason that we know of why FSFS deployed with
> similar care and consideration on NFS would suffer from reliability
> or performance problems, but
> * we make no explicit claims about the viability of any approach
> other than our own.


> So, CollabNet's choice of BDB is not a vote of no confidence in FSFS. Most
> of CollabNet's present and past Subversion developers (myself included) use
> FSFS for our own repositories because it works great and is a better fit for
> our own deployment scenarios (which typically don't include a team of
> world-class CollabNet sysadmins). :-)
> Just for kicks, I wrote a little shell script to do 3 svnadmin load's (very
> write-centric) and 3 svnadmin verify's (very read-centric) on the various
> combinations of BDB vs. FSFS and local-disk vs. NFS-hosted. Here are the
> results (as averages ... the variations were small enough to be insignificant):
> svnadmin load of the first 500 revisions of The Subversion Source
> Code Repository (from a local-disk-stored dumpfile):
> +---------+---------+
> NFS | 48.101s | 99.957s |
> +---------+---------+
> LOCAL | 71.676s | 65.633s |
> +---------+---------+
> svnadmin verify of the repository freshly-loaded with those first
> 500 revisions:
> +---------+---------+
> NFS | 8.369s | 24.183s |
> +---------+---------+
> LOCAL | 8.045s | 6.659s |
> +---------+---------+
> Do what you will with these numbers. (I admit being shocked by the BDB-NFS
> vs. BDB-LOCAL "load" numbers ... maybe reading the dumpfile and loading into
> a repos on the same local hard-drive causes too much disk churn?)

I'll do some tests of my own when we get our new hardware setup.

Thanks for the reply.


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Received on Fri Mar 9 16:52:02 2007

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