Yes. And Patrick's experience is not unexpected. There is, however, a huge variation with different types of flash memory. The software driving the flash can also result in very different experience. The experiences that he alludes to are likely with a conventional SSD packaging of flash driven via the normal block device emulator. That can be substantially sub-optimal, depending on which vendor and configuration you use.
On Thu, Oct 4, 2012 at 5:12 AM, Jun Rao <jun...@gmail.com> 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 <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 > > >
