Re: Sudden Query slowdown on our Postgresql Server

Hi,

unfortunately we cannot directly control the TRIM (i am not sure it even occurs) because the SSDs are behind an LSI
MegaSAS9260 Controller which does not allow access via smart. Even if some kind of TRIM command is the problem,
shouldn'tthe iowait go up in this case? 

Sebastian

On 23.03.2012, at 08:10, Yeb Havinga wrote:

> On 2012-03-23 05:53, Sebastian Melchior wrote:
>> Hi,
>>
>> we already used iostat and iotop during times of the slowdown, there is no sudden drop in I/O workload in the times
ofthe slowdown. Also the iowait does not spike and stays as before. 
>> So i do not think that this is I/O related. As the disks are SSDs there also still is some "head room" left.
>
> I've seen a ssd completely lock up for a dozen seconds or so after giving it a smartctl command to trim a section of
thedisk. I'm not sure if that was the vertex 2 pro disk I was testing or the intel 710, but enough reason for us to not
mountfilesystems with -o discard. 
>
> regards,
> Yeb
>
>
>
>
> --
> Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-performance