On Apr 13, 2010, at 9:31 AM, till wrote: > Hey devs, > > I'm trying to compact a production database here (in hope to recover > some space), and made the following observations: > > * the set is 212+ million docs > * currently 0.8 TB in size > * the instance (XL) has 2 cores, one is idle, the other maybe utilized at 10% > * memory - 2 of 15 GB taken, no spikes > * io - well it's EBS :( > > When I started _compact read operations slowed down (I'll give you 20 > Mississippi's for something that loads instantly otherwise). > Everything "eventually" worked, but it slowed down tremendously. > > I restarted the CouchDB process and everything is back to "snap". > > Does anyone have any insight on why that is the case?
I'm guessing this is an EBS / EC2 issue. You are probably saturating the IO pipeline. It's too bad there's not an easy way to 'nice' the compaction IO. If you got unlucky and are on a particularly bad EBS / EC2 instance, you might do best to start up a new Couch in the same availability zone and replicate across to it. This will accomplish more-or-less the same effect as compaction. > > Till
