From: Florian Weimer <fweimer@bfk.de>
To: Arjen van der Meijden <acmmailing@tweakers.net>
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Harsh Azad <harsh.azad@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: SAN vs Internal Disks
Date: Fri, 07 Sep 2007 10:14:50 +0200
Message-ID: <82myvynb7p.fsf@mid.bfk.de> (raw)
In-Reply-To: <46E0571A.7000102@tweakers.net>
References: <a199704d0709060535q6fea139aq2e3863e685555b0d@mail.gmail.com>
<dcc563d10709060925o6f11f632sbfbc2b64530ae80d@mail.gmail.com>
<a199704d0709061003u71d536fbh9d71ed095dfe16b@mail.gmail.com>
<dcc563d10709061107q7177441elcd6fd8c45fdecce3@mail.gmail.com>
<a199704d0709061115q7949a644kc13961ed43da3b0a@mail.gmail.com>
<dcc563d10709061142o62747836p22c4c53af3d5500d@mail.gmail.com>
<46E0571A.7000102@tweakers.net>
* Arjen van der Meijden:
> The disadvantage of using Areca or 3Ware is obviously the lack of
> support in A-brand servers and the lack of support for SAS-disks. Only
> recently Areca has stepped in the SAS-market, but I have no idea how
> easily those controllers are integrated in standard servers (they tend
> to be quite large, which will not fit in 2U and maybe not even in 3U
> or 4U-servers).
Recent 3ware controllers are a bit on the hot side, too. We had to
switch from two 12 port controllers to a single 24 port controller
because of that (combined with an unlucky board layout: the two 8x
PCIe connectors are next to each other).
Unfortunately, read performance maxes out at about 8 disks in a
RAID-10 configuration. Software RAID-0 across hardware RAID-1 is
significantly faster (factor of 3 to 5 in low-level benchmarks).
However, it seems that something in this stack does not enforce write
barriers properly, so I don't think we will use this in production.
RAID-6 doesn't perform well, either (especially for several processes
reading different files sequentially).
We'll probably split the 24 disks into a couple of RAID-10s, and
distribute tables and indexes manually among the file systems. This
is a bit disappointing, especially because the system is able to read
at 800+ MB/s, as shown by the software-RAID-on-hardware-RAID
configuration.
I haven't seen 24-disk benchmarks with Areca controllers. A
comparison might be interesting.
--
Florian Weimer <fweimer@bfk.de>
BFK edv-consulting GmbH http://www.bfk.de/
Kriegsstraße 100 tel: +49-721-96201-1
D-76133 Karlsruhe fax: +49-721-96201-99
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: fweimer@bfk.de, acmmailing@tweakers.net, scott.marlowe@gmail.com, harsh.azad@gmail.com
Subject: Re: SAN vs Internal Disks
In-Reply-To: <82myvynb7p.fsf@mid.bfk.de>
* 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