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From Jean-Yves Moulin <...@baaz.fr>
Subject couchdb performances
Date Thu, 14 Feb 2013 17:51:11 GMT
Hi everybody,

I've a performance issue on my CouchDB servers.

My OS is a FreeBSD-8.3 with ZFS. My ZFS pool is a raid10 array (two concatenated mirror),
using four 7.2K SATA Disk and a SSD for the ZIL (== write cache). I'm using CouchDB-1.2.0.

My database, before compaction, is 1TB with 91M documents. CouchDB says there is 90GB of data
(~1KB per doc).


When running compaction, CouchDB takes very little CPU (~20% of one processor for beam.smp)
and reads very slowly: 800KB/s (~200KB/s per disk, small transactions rate). Compaction takes
days...

That is really strange because I'm able to read my full database, with dd, at a better speed:
80MB/s (~20MB/s per disk and bigger transactions rate) not perfect but quicker than CouchDB.

What can make CouchDB read so slowly ? Does anybody have an idea about this slowness ?

thank you for your help.

Best,
jym

PS: We plan to use CouchDB in a write-heavy application: 500 doc inserted by seconds, only
one simple view. Servers will be bigger (12 or 24 disks, SSD for cache) and the bigcouch merge
will be a great help but we need better performance on a single node while waiting the 2.0
release :-)
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