On Tue, May 4, 2010 at 11:34 AM, Brandon High <bh...@freaks.com> wrote:
> On Tue, May 4, 2010 at 10:19 AM, Tony MacDoodle <tpsdoo...@gmail.com> > wrote: > > How would one determine if I should have a separate ZIL disk? We are > using > > ZFS as the backend of our Guest Domains boot drives using LDom's. And we > are > > seeing bad/very slow write performance? > > There's a dtrace script that Richard Elling wrote called zilstat.ksh. > It's available at > http://www.richardelling.com/Home/scripts-and-programs-1/zilstat > > I'm not sure what the numbers mean (there's info at the address) but > anything other than lots of 0s indicates that the ZIL is being used. On my workstation, I peg my IOPS when using VirtialBox set to run on zvols. The zilstat line comes back with about 3000 total synchronous writes per 30sec. Which means that my disks are doing about 90 sync IOPS write. That is about the upper limit for 7200rpm disks ( from what I understand ). This 3000 number doesn't really change much over time when running with IO load. Disabling the ZIL, I get much better performance, in terms of IO throughput. This tells me that the ZIL is the bottleneck. I will be getting an SSD soon. -- Marc
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