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From Tyler Gillies <ty...@pdxbrain.com>
Subject Re: Which filesystem is best for deploying couchdb and why?
Date Fri, 17 Sep 2010 01:22:18 GMT
Wow, thanks for the thought out writeup!

On Thu, Sep 16, 2010 at 12:47 PM, Randall Leeds <randall.leeds@gmail.com>wrote:

> Disclaimer: I'm no file systems expert.
>
> I recommend something with extents otherwise you might take a big
> performance hit while couch deletes old db files after compaction.
> Compression sounds cool as long as you can do it really fast (are
> there setups where this happens in hardware?).
>
> reiserfs:
> According to wikipedia it "still uses the big kernel lock (BKL) — a
> global kernel-wide lock" which makes performance on multiple cores
> suffer.
> It's big benefit, as I always understood it, is being able to pack
> smile files together into single blocks. You will likely not have lots
> of small files with Couch :-P
>
> xfs:
> Delayed allocation might be a big performance win with a Couch. Since
> outstanding writes are committed together in chunks and then fsync'd
> all together I bet this feature would do good things for Couch
> performance.
>
> ext(3|4)
> I'd recommend ext4 over ext3. Delayed allocation like xfs as well as
> the multiblock allocator should make it much better than ext3. You
> also get extents.
>
> btrfs/zfs:
> Some of the features of each sound interesting, but nothing that
> stands out to me as "great for CouchDB". Snapshots and backups are
> cool, but Couch is doing this for you already in a sense due to the
> way the btree is appended: CouchDB documents are, in a sense,
> copy-on-write. Checksumming is cool if you think it's important for
> your data integrity. If you want snapshots for backup you can always
> use CouchDB replication.
>
> If you run any tests I'd be very, very interested in seeing your results.
>
> -Randall
>
> On Thu, Sep 16, 2010 at 03:11, Metin Akat <akat.metin@gmail.com> wrote:
> > I'm sure almost everybody out there is using ext4/3 (including me),
> > but what about filesystems like btrfs, zfs, reiserfs, xfs. Some of
> > them have very appealing feature-sets (like compression for example,
> > and we all know how greedy is couchdb for disk space).
> > And I know that for example btrfs is not yet "recommended for
> > production". But its time is coming. From what I see, Ubuntu 10.10
> > works flawlessly on btrfs.
> > So I'd be happy if we have some discussion on the topic, instead of
> > "everybody uses ext4, just use it" kind of stuff :).
> > Couchdb was "alpha software" for years, and we all used it in
> > production, so we are not afraid of alpha/beta software, as long as
> > it's good :)
>



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