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List:       zfs-discuss
Subject:    Re: [zfs-discuss] Sun T3-2 and ZFS on JBODS
From:       Marion Hakanson <hakansom () ohsu ! edu>
Date:       2011-03-06 22:23:34
Message-ID: 201103062223.p26MNYBm013842 () kyklops ! ohsu ! edu
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sigbjorn@nixtra.com said:
> I will do some testing on the loadbalance on/off. We have nearline SAS disks,
> which does have dual path from the disk, however it's still just 7200rpm
> drives.
> 
> Are you using SATA , SAS or SAS-nearline in your array? Do you have multiple
> SAS connections to your arrays, or do you use a single connection per array
> only? 

We have four Dell MD1200's connected to three Solaris-10 systems.  Three
of the MD1200's have nearline-SAS 2TB 7200RPM drives, and one has SAS 300GB
15000RPM drives.  All the MD1200's are connected with dual SAS modules to
a dual-port HBA on their respective servers (one setup is with two MD1200's
daisy-chained, but again using dual SAS modules & cables).

Both types of drives suffer super-slow writes (but reasonable reads) when
loadbalance=roundrobin is in effect.  E.g 280 MB/sec sequential reads, and
28MB/sec sequential writes, for the 15kRPM SAS drives I tested last week.
We don't see this extreme slowness on our dual-path Sun J4000 JBOD's, but
those all have SATA drives (with the dual-port interposers inside the
drive sleds).

Regards,

Marion


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