On Wed, Oct 3, 2012 at 9:12 PM, Jun Rao <jun...@gmail.com> wrote: > Patrick, > > Thanks for the info. Does each ZK write wait for log being flushed to disk? >
Yes (it's necessary for the guarantees we provide), although the servers do batching of writes to improve throughput. This doc gives some insight: http://zookeeper.apache.org/doc/r3.4.4/zookeeperOver.html#Performance Patrick > On Wed, Oct 3, 2012 at 6:13 PM, Patrick Hunt <ph...@apache.org> 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 <jun...@gmail.com> 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 >>
