On Apr 6, 2012, at 4:58 PM, Marion Hakanson wrote:

> a...@blackandcode.com said:
>> I'm spec'ing out a Thumper-esque solution and having trouble finding my
>> favorite Hitachi Ultrastar 2TB drives at a reasonable post-flood price. The
>> Seagate Constellations seem pretty reasonable given the market circumstances
>> but I don't have any experience with them. Anybody using these in their ZFS
>> systems and have you had good luck?  
> We have a lot of 2TB and 3TB Seagates here, they work fine.  Most of
> ours are the Nearline-SAS variety, in Dell MD1200 enclosures, used on
> Windows & Linux behind PERC H800 RAID cards, and on Solaris-10 and
> OpenIndiana behind LSI SAS HBA's.  We do have one new server with a
> pile of 2TB SATA Seagate's as well, so far working fine.
> The only caveat I've found is that the Nearline SAS Seagates go really
> slow with the Solaris default multipath load-balancing setting
> (round-robin).  Set it to "none" or some large block value and they go
> fast.  This issue doesn't appear when used with the PERC H800's.

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 
driver. Both of these are being tracked as https://www.illumos.org/issues/644 
there is an alternate scsi_vhci.conf file posted in that bugid.

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.
 -- richard

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