Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TiajU-0005Qb-Dv for pgsql-performance@arkaria.postgresql.org; Wed, 12 Dec 2012 01:03:32 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.72) (envelope-from ) id 1TiajT-00087Q-Uu for pgsql-performance@arkaria.postgresql.org; Wed, 12 Dec 2012 01:03:31 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TiajT-00087L-3S for pgsql-performance@postgresql.org; Wed, 12 Dec 2012 01:03:31 +0000 Received: from outmail148102.authsmtp.net ([62.13.148.102]) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TiajN-00033H-Sk for pgsql-performance@postgresql.org; Wed, 12 Dec 2012 01:03:30 +0000 Received: from mail-c232.authsmtp.com (mail-c232.authsmtp.com [62.13.128.232]) by punt7.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id qBC13M6e059544; Wed, 12 Dec 2012 01:03:22 GMT Received: from ayaki.localdomain (58-7-194-83.dyn.iinet.net.au [58.7.194.83]) (authenticated bits=0) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id qBC13FCn020966 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Wed, 12 Dec 2012 01:03:18 GMT Message-ID: <50C7D7D2.4070605@2ndQuadrant.com> Date: Wed, 12 Dec 2012 09:03:14 +0800 From: Craig Ringer Organization: 2nd Quadrant User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Evgeny Shishkin CC: =?windows-1252?Q?Niels_Kristian_Schj=F8dt?= , Jeff Janes , "pgsql-performance@postgresql.org" Subject: Re: Do I have a hardware or a software problem? References: <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> In-Reply-To: X-Enigmail-Version: 1.4.6 Content-Type: multipart/alternative; boundary="------------080501050005020207080709" X-Server-Quench: b8775cce-43f7-11e2-b10b-0025903375e2 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCdxZQATClZeVg0b BQteCiN5VAwpPBRK HVkIKg5MJUcNSQVJ NksachtFaQdbaVxS HGQLWlZEUFx7WWB/ aQofaA1DZVRPVgF0 WEtWQFdQERppT11z dR8dJGosdwdGcXh2 K0RlXXNeEhZyckF4 ER0BCGkFM2B9aWFK Ul0KdgMGbQNKfBpM alN8U3ZYYytlM3Bw LDceBR4WBxBqYAhS CiBFLVsMTA4CVj41 XRwdFC8iVUofDyx7 NBsoNkEVBktZKl81 O18sXAVw X-Authentic-SMTP: 61633235383639.1019:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 58.7.194.83/2525 X-AuthVirus-Status: No virus detected - but ensure you scan with your own anti-virus system. X-Pg-Spam-Score: -2.6 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org This is a multi-part message in MIME format. --------------080501050005020207080709 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by punt7.authsmtp.com id qBC13M6e059544 On 12/12/2012 06:44 AM, Evgeny Shishkin wrote: > > On Dec 12, 2012, at 2:41 AM, Niels Kristian Schj=F8dt > > wrot= e: > >> 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. --=20 Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services --------------080501050005020207080709 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by punt7.authsmtp.com id qBC13M6e059544
On 12/12/2012 06:44 AM, Evgeny Shishki= n wrote:

On Dec 12, 2012, at 2:41 AM, Niels Kristian Schj=F8dt <nielskristian@aut= ouncle.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.

--=20
 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services
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