Re: Performances issues with SSD volume ?

> From: Koray Eyidoğan <korayey(at)gmail(dot)com>
>To: Thomas SIMON <tsimon(at)neteven(dot)com>
>Cc: pgsql-admin(at)postgresql(dot)org
>Sent: Monday, 18 May 2015, 14:51
>Subject: Re: [ADMIN] Performances issues with SSD volume ?
>
>
>
>Hi Thomas,
>
>
>3.2 kernel may be #1 cause of your I/O load problem:
>
>
>http://www.databasesoup.com/2014/09/why-you-need-to-avoid-linux-kernel-32.html
>
>https://medium.com/postgresql-talk/benchmarking-postgresql-with-different-linux-kernel-versions-on-ubuntu-lts-e61d57b70dd4
>
>
>
>Have a nice day.
>
>
>Koray

Likely 3.2 kernel isn't helping, but I think we need much more information before jumping to conclusions.

You say you're IO bound, so some output from sar / iostat / dstat and pg_stat_activity etc before and during the issue would be of use.

Also:
System memory size

SSD Model numbers and how many
Raid controller
Partition allignments and stripe sizes
Kernel options
Filesystem used and mount options
IO Scheduler
Postgresql version and configuration
Connection pool sizing

Perhaps you could thow us the output of some of these:

fdisk -l
cat /etc/mtab
cat /sys/block/<ssd device>/queue/scheduler
sysctl kernel | grep sched
sysctl vm
select * from pg_stat_activity
select name, setting from pg_settings
lspci | grep -E 'RAID|SCSI|IDE|SATA'