Re: H800 + md1200 Performance problem

On Tue, Apr 3, 2012 at 6:20 AM, Cesar Martin <cmartinp(at)gmail(dot)com> wrote:
> Hello there,
>
> I am having performance problem with new DELL server. Actually I have this
> two servers
>
> Server A (old - production)
> -----------------
> 2xCPU Six-Core AMD Opteron 2439 SE
> 64GB RAM
> Raid controller Perc6 512MB cache NV
>   - 2 HD 146GB SAS 15Krpm RAID1 (SO Centos 5.4 y pg_xlog) (XFS no barriers)
>   - 6 HD 300GB SAS 15Krpm RAID10 (DB Postgres 8.3.9) (XFS no barriers)
>
> Server B (new)
> ------------------
> 2xCPU 16 Core AMD Opteron 6282 SE
> 64GB RAM
> Raid controller H700 1GB cache NV
>   - 2HD 74GB SAS 15Krpm RAID1 stripe 16k (SO Centos 6.2)
>   - 4HD 146GB SAS 15Krpm RAID10 stripe 16k XFS (pg_xlog) (ext4 bs 4096, no
> barriers)
> Raid controller H800 1GB cache nv
>   - MD1200 12HD 300GB SAS 15Krpm RAID10 stripe 256k (DB Postgres 8.3.18)
> (ext4 bs 4096, stride 64, stripe-width 384, no barriers)
>
> Postgres DB is the same in both servers. This DB has 170GB size with some
> tables partitioned by date with a trigger. In both shared_buffers,
> checkpoint_segments... settings are similar because RAM is similar.
>
> I supposed that, new server had to be faster than old, because have more
> disk in RAID10 and two RAID controllers with more cache memory, but really
> I'm not obtaining the expected results

What does

sysctl -n vm.zone_reclaim_mode

say? If it says 1, change it to 0:

sysctl -w zone_reclaim_mode=0

It's an automatic setting designed to make large virtual hosting
servers etc run faster but totally screws with pg and file servers
with big numbers of cores and large memory spaces.