[OmniOS-discuss] iSCSI traffic suddenly comes to a halt and then resumes

[Narayan Desai]

And, if you don't have the luxury of discarding hardware and replacing it
with a supported configuration, you might look at finding marginal drives,
either via error counters displayed in iostat -En, or drives with really
high service times (in iostat -xnz output). We found (on a similar setup),
that being really aggressive about drive replacement helped a lot.

If you have desktop sata drives, then the drive firmware is part of the
problem. Desktop drives retry for quite a long time when they encounter
errors, which produce really inconsistent performance profiles. When you
aggregate into a raid set (including in ZFS) tail latencies really start to
matter for performance, and the pool just starts going out to lunch for a
long time. If you can figure out and replace the drive is causing the
problem (even if it isn't causing any hard errors), the pool performance
goes back to normal.
 -nld

On Tue, May 5, 2015 at 4:21 AM, <mir at miras.org> wrote:

> On 2015-05-05 09:46, Matej Zerovnik wrote:
>
>>
>> We still kept our SATA hard drives in Supermicro JBOD with SAS
>> expander and SATA drives.
>>
>>  Your problem boils down to using SATA disks in a SAS expander. Search
> omnios user list and you will find numerous proofs that using SATA disks in
> a SAS expander causes weird behaviors and instability.
>
> The fact is that SATA disks is unsupported in a SAS expander due to
> incompatibility between command sets in SAS and SATA. As an example SATA
> NCQ is not passed through the SAS expander which might could be the cause
> of your strange iSCSI disconnects experienced on the client side.
>
> ----
>
> This mail was virus scanned and spam checked before delivery.
> This mail is also DKIM signed. See header dkim-signature.
>
>
> _______________________________________________
> OmniOS-discuss mailing list
> OmniOS-discuss at lists.omniti.com
> http://lists.omniti.com/mailman/listinfo/omnios-discuss
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://omniosce.org/ml-archive/attachments/20150505/54b21dae/attachment.html>