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List:       zfs-discuss
Subject:    Re: [zfs-discuss] Seagate Constellation vs. Hitachi Ultrastar
From:       Anh Quach <anh () blackandcode ! com>
Date:       2012-04-10 0:42:57
Message-ID: 08D78556-BCD3-4408-83D5-9F09B1EBF3A6 () blackandcode ! com
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Are these issues something to watch out for on Solaris 11 as well? Thx in a=
dvance=85

-Anh


On Apr 9, 2012, at 12:43 PM, Marion Hakanson wrote:

> richard.elling@richardelling.com said:
>> We are starting to see a number of SAS HDDs that prefer logical-block to
>> round-robin. I see this with late model Seagate and Toshiba HDDs.
>> =

>> There is another, similar issue with recognition of multipathing by the
>> scsi_vhci driver. Both of these are being tracked as https://www.illumos=
.org/
>> issues/644 and there is an alternate scsi_vhci.conf file posted in that
>> bugid.
> =

> Interesting, I just last week had a Toshiba come from Dell as a replaceme=
nt
> for a Seagate 2TB SAS drive;  On Solaris-10, the Toshiba insisted on show=
ing
> up as 2 drives, so mpxio was not recognizing it.  Fortunately I was able =
to
> swap the drive for a Seagate, but I'll stash away a copy of the scsi_vhci=
.conf
> entry for the future.
> =

> =

>> We're considering making logical-block the default (as in above bugid) a=
nd we
>> have not discovered a reason to keep round-robin. If you know of any rea=
son
>> why round-robin is useful, please add to the bugid. =

> =

> Should be fine.  When I first ran into this a couple years ago, I did a
> lot of tests and found logical-block to be slower than "none" (with those
> Seagate 2TB SAS drives in Dell MD1200's), but not a whole lot slower.
> I vaguely recall that round-robin was better for highly random, small I/O =

> (IOPS-intensive) workloads.
> =

> I got the best results by manually load-balancing half the drives to one
> path and half the drives to the other path.  But I decided it was not
> worth the effort.  Maybe if there was a way to automatically do that
> (with a relatively static result)....  Of course, this was all tested
> on Solaris-10, so your mileage may vary.
> =

> Regards,
> =

> Marion
> =

> =


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