Disabling the ZIL will cause synchronous writes to occur asynchronously. If any applications depend upon the use of synchronous writes for their correctness, they're likely to be adversely affected.
There are a number of ZIL performance fixes that have been checked in recently, or that are in the pipeline. So, if you do decide to disable the ZIL be sure to do so on a temporary basis. While disabling the ZIL may improve performance in some cases, there's a corner-case affecting filesystem flush where ZFS must wait. In this situation the ZIL is typically committed; however, if one is not present ZFS must issue a txg_wait_synced() and wait for transactions on that objectset to complete. This is pretty rare, though. (And also quite different from VOP_FSYNC / O_DSYNC). The author of the ZIL has a good blog entry about its overall design, for those curious. It's available from here: http://blogs.sun.com/perrin/entry/the_lumberjack -j On Mon, Oct 02, 2006 at 03:57:08PM -0700, William D. Hathaway wrote: > Hi Ben, > I second the notion to ask in zfs-discuss, but I did see a thread on > the Yahoo Solaris x86 group that seemed similar to your question. I > think the main work-around was echo "zil_disable/W 1" | mdb -kw > > (which apparently has some side effects regarding syncing). You can > view the message and thread at > http://tech.groups.yahoo.com/group/solarisx86/message/39057 > > --Bill > > > This message posted from opensolaris.org > _______________________________________________ > perf-discuss mailing list > perf-discuss@opensolaris.org _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
