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From Wout Mertens <>
Subject Re: Which filesystem is best for deploying couchdb and why?
Date Mon, 20 Sep 2010 13:32:18 GMT
On Sep 19, 2010, at 9:42 , Metin Akat wrote:

> Hmm, then I start thinking that btrfs is really better than ext4,
> especially if I want to do things like copy the files in order to
> deploy (fast) another instance with already build view indexes.

Well, ext4 is considered more stable than btrfs, that has to count for something in your reasoning

How would btrfs help with fast copies? You would still need to transfer the files to another
system, no?

> And would the couchdb files compress well?



> On Sat, Sep 18, 2010 at 12:23 PM, Wout Mertens <> wrote:
>> Everything except the 4KB blocksize I would say. While ZFS and Btrfs are very different
on-disk, they are both Copy-On-Write filesystems with extents, compression and cheap snapshots.
I don't know how the 4KB blocksize settings translates onto Btrfs.
>> They are both really suited for the append-only workload CouchDB presents.
>> Wout.
>> On Sep 18, 2010, at 9:49 , Metin Akat wrote:
>>> What part of this blog post is relevant to btrfs?
>>> On Fri, Sep 17, 2010 at 10:22 PM, Chris Anderson <> wrote:
>>>> On Thu, Sep 16, 2010 at 6:22 PM, Tyler Gillies <>
>>>>> Wow, thanks for the thought out writeup!
>>>> here's a blog post
>>>>> On Thu, Sep 16, 2010 at 12:47 PM, Randall Leeds <>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) —
>>>>>> 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
>>>>>> 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
>>>>>> 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
>>>>>> -Randall
>>>>>> On Thu, Sep 16, 2010 at 03:11, Metin Akat <>
>>>>>>> I'm sure almost everybody out there is using ext4/3 (including
>>>>>>> but what about filesystems like btrfs, zfs, reiserfs, xfs. Some
>>>>>>> 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
>>>>>>> works flawlessly on btrfs.
>>>>>>> So I'd be happy if we have some discussion on the topic, instead
>>>>>>> "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
>>>>>>> it's good :)
>>>>> --
>>>>> Ask me anything <>!
>>>> --
>>>> Chris Anderson

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