On Fri, Jun 11, 2010 at 1:26 PM, Robert Milkowski <mi...@task.gda.pl> wrote:
> On 11/06/2010 09:22, sensille wrote: > >> Andrey Kuzmin wrote: >> >> >>> On Fri, Jun 11, 2010 at 1:54 AM, Richard Elling >>> <richard.ell...@gmail.com<mailto:richard.ell...@gmail.com>> wrote: >>> >>> On Jun 10, 2010, at 1:24 PM, Arne Jansen wrote: >>> >>> > Andrey Kuzmin wrote: >>> >> Well, I'm more accustomed to "sequential vs. random", but YMMW. >>> >> As to 67000 512 byte writes (this sounds suspiciously close to >>> 32Mb fitting into cache), did you have write-back enabled? >>> > >>> > It's a sustained number, so it shouldn't matter. >>> >>> That is only 34 MB/sec. The disk can do better for sequential >>> writes. >>> >>> Note: in ZFS, such writes will be coalesced into 128KB chunks. >>> >>> >>> So this is just 256 IOPS in the controller, not 64K. >>> >>> >> No, it's 67k ops, it was a completely ZFS-free test setup. iostat also >> confirmed >> the numbers. >> > > It's a really simple test everyone can do it. > > # dd if=/dev/zero of=/dev/rdsk/cXtYdZs0 bs=512 > > I did a test on my workstation a moment ago and got about 21k IOPS from my > sata drive (iostat). > The trick here of course is that this is sequentail write with no other > workload going on and a drive should be able to nicely coalesce these IOs > and do a sequential writes with large blocks. Exactly, though one might still wonder where the coalescing actually happens, in the respective OS layer or in the controller. Nonetheless, this is hardly a common use-case one would design h/w for. Regards, Andrey > > > > -- > Robert Milkowski > http://milek.blogspot.com > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
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