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<p><tt><font size="2">"Schweiss, Chip" <chip@innovates.com> wrote on 09/28/2014 10:07:15 AM:<br>
> <br>
> On 26/09/2014 00:46, Andrew M. Hettinger wrote:</font></tt><br>
<tt><font size="2">>> I'm presently running tests on a pool using 3x Samsung 850 SSDs on a<br>
>> LSI-9211-8i<br>
>> (IT) contoller. I thought I'd try seperating the intent log to see if lowering<br>
>> the write amplification on the pool-drives would help, so I added another<br>
>> matching SSD for that, but under load I still seem to get extensive checksum<br>
>> errors. Does anyone have any ideas as to what would be causing this?<br>
</font></tt><br>
<tt><font size="2">> <br>
> I would suspect hardware. Avoid overly cheap SAS cables.</font></tt><br>
<br>
<tt><font size="2">I'll try it in another machine as soon as I can, but it seems to work fine with spinning HDs.</font></tt><br>
<tt><font size="2"><br>
> <br>
> I run nearly 100 SSDs with Illumos based ZFS. 63 of them are <br>
> Samsung 840 Pros in a pure SSD pool in a Supermicro JBOD. I don't <br>
> see any checksum problems. <br>
</font></tt><br>
<tt><font size="2">> The 850 has the same firmware as the 840 so the new generation <br>
> should not make any difference.</font></tt><br>
<tt><font size="2">> <br>
> I also always run SAS to SATA interposers to keep the SAS buses <br>
> happy. However, Samsung SSDs are the only brand SSD that I found <br>
> to consistently work with the interposers.</font></tt><br>
<br>
<tt><font size="2">Can you link me to the interposers? I wonder if that would make a difference.</font></tt><br>
<tt><font size="2"><br>
> <br>
> All my HBAs are LSI 2308 and 2008 controller based. Make sure your<br>
> firmware is up to date. There have been many SSD related fixes in <br>
> the LSI HBA. <br>
</font></tt><br>
<tt><font size="2">Firmware is current. I checked LSI's site last week.</font></tt><br>
<br>
<tt><font size="2">> If you can avoid it don't use a SAS expander, they will slow things <br>
> down and without interposers are susceptible to reset storms. </font></tt><br>
<br>
<tt><font size="2">There is no SAS expanders involved.<br>
</font></tt><br>
<tt><font size="2">> A log device is really necessary on an SSD pool. The sync write <br>
> behavior of ZFS simply does not work well with SSDs with out a log. <br>
> Using an 850 is not a good choice for a log device because it does<br>
> not have power loss protections. You are better off turning sync off<br>
> than trying to use them as a log. </font></tt><br>
<br>
<tt><font size="2">Can you make a recommendation for the slog?</font></tt><br>
<br>
<tt><font size="2">> <br>
> -Chip </font></tt><br>
<br>
<tt><font size="2">Thanks for everyone's help here!</font></tt></body></html>