richard.ell...@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 replacement for a Seagate 2TB SAS drive; On Solaris-10, the Toshiba insisted on showing 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) and we > have not discovered a reason to keep round-robin. If you know of any reason > 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 _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
