From: Craig Ringer <craig@2ndQuadrant.com>
To: Evgeny Shishkin <itparanoia@gmail.com>
Cc: Niels Kristian Schjødt <nielskristian@autouncle.com>
Cc: Jeff Janes <jeff.janes@gmail.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Do I have a hardware or a software problem?
Date: Wed, 12 Dec 2012 09:03:14 +0800
Message-ID: <50C7D7D2.4070605@2ndQuadrant.com> (raw)
In-Reply-To: <ED7DEE06-B822-43E0-AF49-D89BB40C4C83@gmail.com>
References: <AE27BD07-7A3A-449A-BD3F-A0DF4EF76C04@autouncle.com>
<CAMkU=1zcXD5YWMD=QOAdoNG0BKoB-DAXKbzBKybE-3w-YzhSgw@mail.gmail.com>
<8F7661E7-D6D4-4334-8C6A-A8B6C56A2C3F@autouncle.com>
<50C7351C.30407@2ndQuadrant.com>
<4507A68A-3CD5-4283-AFA5-1C0593427E14@autouncle.com>
<67FBF3AF-5C6A-45D4-9206-7257C8C01C5E@gmail.com>
<CADZnK0nmm=2WnVVsveu3j0sJ95Ct13SqKbjQ_9DeVCGAmrcggw@mail.gmail.com>
<E2A43856-FE0A-44BC-9764-C3CA533D94D9@gmail.com>
<CADZnK0=0q9Ti9jVpCX3VX=3X_Rs=AxONhxC9cejnbOd5GKjb4A@mail.gmail.com>
<ED7DEE06-B822-43E0-AF49-D89BB40C4C83@gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-performance>
On 12/12/2012 06:44 AM, Evgeny Shishkin wrote:
>
> On Dec 12, 2012, at 2:41 AM, Niels Kristian Schjødt
> <nielskristian@autouncle.com <mailto:nielskristian@autouncle.com>> wrote:
>
>> Are you using a hardware based raid controller with them?
>>
> Yes, of course. Hardware raid with cache and bbu is a must. You can't
> get fast fsync without it.
Most SSDs should offer fairly fast fsync without a hardware RAID
controller, as they do write-back caching. The trick is to find ones
that do write-back caching safely, so you don't get severe data
corruption on power-loss.
A HW RAID controller is an absolute must for rotating magnetic media,
though.
> Also mdadm is a pain in the ass and is suitable only on amazon and
> other cloud shit.
I've personally been pretty happy with mdadm. I find the array
portability it offers very useful, so I don't need to buy a second RAID
controller just in case my main controller dies and I need a compatible
one to get the array running again. If you don't need a BBU for safe
write-back caching then mdadm has advantages over hardware RAID.
I'll certainly use mdadm over onboard fakeraid solutions or low-end
hardware RAID controllers. I suspect a mid- to high end HW RAID unit
will generally win.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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: craig@2ndQuadrant.com, itparanoia@gmail.com, nielskristian@autouncle.com, jeff.janes@gmail.com
Subject: Re: Do I have a hardware or a software problem?
In-Reply-To: <50C7D7D2.4070605@2ndQuadrant.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