From: Tomas Vondra <tv@fuzzy.cz>
To: Cody Caughlan <toolbag@gmail.com>
Cc: Tomas Vondra <tv@fuzzy.cz>
Cc: pgsql-performance@postgresql.org
Subject: Re: Slow queries / commits, mis-configuration or hardware issues?
Date: Wed, 16 Nov 2011 03:16:15 +0100
Message-ID: <c22ff328a0f3e8d1ddd013aa8913dd09.squirrel@sq.gransy.com> (raw)
In-Reply-To: <CAPVp=gY-RrkhPQNRMMFcx5CZhJqiZeYh32W2p6Tvj9FsepGJmA@mail.gmail.com>
References: <CAPVp=gYs7uYF_hy0MDBkpRCxNbWQHPSyP6sXO-6SJZ_TvaU=XQ@mail.gmail.com>
<87e450fd65045c328f41e1b99a4029d5.squirrel@sq.gransy.com>
<CAPVp=ga6CkO8vXJJs5PswKv0Cf3R3SpUK+KmQXY8edpc84CddA@mail.gmail.com>
<4EC30F05.6010901@fuzzy.cz>
<CAPVp=gY-RrkhPQNRMMFcx5CZhJqiZeYh32W2p6Tvj9FsepGJmA@mail.gmail.com>
On 16 Listopad 2011, 2:21, Cody Caughlan wrote:
> How did you build your RAID array? Maybe I have a fundamental flaw /
> misconfiguration. I am doing it via:
>
> $ yes | mdadm --create /dev/md0 --level=10 -c256 --raid-devices=4
> /dev/xvdb /dev/xvdc /dev/xvdd /dev/xvde
> $ pvcreate /dev/md0
> $ vgcreate lvm-raid10 /dev/md0
> $ lvcreate -l 215021 lvm-raid10 -n lvm0
> $ blockdev --setra 65536 /dev/lvm-raid10/lvm0
> $ mkfs.xfs -f /dev/lvm-raid10/lvm0
> $ mkdir -p /data && mount -t xfs -o noatime /dev/lvm-raid10/lvm0 /data
>
> --
I don't think you have a flaw there. The workload probably skews the
results a bit on the master and slave, so it's difficult to compare it to
results from an idle instance. The amount of data written seems small, but
a random i/o can saturated the devices quite easily.
I went with a very simple raid config - no LVM, default stripe size
(better seeks, worse sequential performance), default read-ahead (could
give better seq. performance).
Tomas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: tv@fuzzy.cz, toolbag@gmail.com
Subject: Re: Slow queries / commits, mis-configuration or hardware issues?
In-Reply-To: <c22ff328a0f3e8d1ddd013aa8913dd09.squirrel@sq.gransy.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox