29.06.2011 16:32, Kevin Wolf wrote: > Am 29.06.2011 14:23, schrieb Anthony Liguori: >> On 06/29/2011 07:16 AM, Kevin Wolf wrote:
>>> No, people are also complaining about bad performance with raw. Which >>> isn't really surprising when you do a flush after each single write >>> request. O_SYNC is really much more than is needed in the average case. >> >> Which file system on the host? > > Honestly, I don't know. Usually the problem is resolved with setting a > different cache option, so nobody bothers to ask for details. I'd guess > that it's ext4 in most cases. Extremly poor performance also happens on raw devices -- be it lvm volumes or plain partitions, so that's w/o any filesystem. Sure, a filesystem adds quite noticeable overhead (because of mtime updates and that sort of things), but _just_ syncronous writes are enough to kill performance. /mjt
