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Zookeeper, mail # user - zookeeper on SSD


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Re: zookeeper on SSD
Milind Parikh 2012-10-04, 04:32
It does seem so.

"The most performance critical part of ZooKeeper is the transaction log.
ZooKeeper syncs transactions to media before it returns a response. A
dedicated transaction log device is key to consistent good performance.
Putting the log on a busy device will adversely effect performance. If you
only have one storage device, put trace files on NFS and increase the
snapshotCount; it doesn't eliminate the problem, but it should mitigate it."
On Oct 3, 2012 9:13 PM, "Jun Rao" <[EMAIL PROTECTED]> wrote:

> Patrick,
>
> Thanks for the info. Does each ZK write wait for log being flushed to disk?
>
> Jun
>
> On Wed, Oct 3, 2012 at 6:13 PM, Patrick Hunt <[EMAIL PROTECTED]> wrote:
>
> > My experience with SSDs and ZK has been discouraging. SSDs have some
> > really terrible corner cases for latency. I've seen them take 40+
> > seconds (that's not a mistake - seconds) for fsync to complete. When
> > this happened (every few hours) all of the sessions would timeout.
> >
> > See this article:
> > http://storagemojo.com/2012/06/07/the-ssd-write-cliff-in-real-life/
> >
> > Patrick
> >
> > On Wed, Oct 3, 2012 at 9:59 AM, Jun Rao <[EMAIL PROTECTED]> wrote:
> > > Hi,
> > >
> > > Will storing the ZK commit log on SSD improve ZK write latency? Does a
> ZK
> > > write wait until data is flushed to disk?
> > >
> > > Thanks,
> > >
> > > Jun
> >
>