Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TibN9-00060Y-J6 for pgsql-performance@arkaria.postgresql.org; Wed, 12 Dec 2012 01:44:31 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.72) (envelope-from ) id 1TibN9-0000Gz-1d for pgsql-performance@arkaria.postgresql.org; Wed, 12 Dec 2012 01:44:31 +0000 Received: from makus.postgresql.org ([98.129.198.125]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TibN7-0000Fs-Hx for pgsql-performance@postgresql.org; Wed, 12 Dec 2012 01:44:29 +0000 Received: from mail-la0-f53.google.com ([209.85.215.53]) by makus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TibN5-0002Zx-NX for pgsql-performance@postgresql.org; Wed, 12 Dec 2012 01:44:28 +0000 Received: by mail-la0-f53.google.com with SMTP id w12so99602lag.40 for ; Tue, 11 Dec 2012 17:44:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :message-id:references:to:x-mailer; bh=TL1UroCm9R1lFzz7UijxLEtD/7aWRQKmlEzmvMt7Ew0=; b=HUqeMQBKA4ap18fxBjn/ywuydnVLfUEaxlrC2p2KDpHXXRGTdasNjuVwpY9DCYafrj M2qmgZPNzfYob/GbaV3LHRAQKM1L6PBr1lp77hbw+fCLakoXbT84gKEMMpSQXePuZ8yI QH0Ygx5bSjbh9t56tLpE85JlYfvOQxAb7KecTHP2D3JwrYlDsTwE1hFhehysHaQjnPj8 rxfepSSGHf1PYZ017wI0AE+F+PsFTVs0efrhds3xpbm//Y5826H4J1GKMiHSvDQESfwi 3d12CN+X2NZCWDkKnlIpoZfqZ2rndS9nf7D6CWWzSeUsIaAFM6vwOIEuI+Ite1mxMetM PYWQ== Received: by 10.112.29.229 with SMTP id n5mr68063lbh.130.1355276665983; Tue, 11 Dec 2012 17:44:25 -0800 (PST) Received: from [192.168.20.5] ([176.195.39.85]) by mx.google.com with ESMTPS id jk8sm9957970lab.7.2012.12.11.17.44.24 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 11 Dec 2012 17:44:25 -0800 (PST) Content-Type: multipart/alternative; boundary="Apple-Mail=_8C3623BB-D898-4B1C-962C-99A01F59D02B" Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: Do I have a hardware or a software problem? From: Evgeny Shishkin In-Reply-To: <50C7DDDE.1000000@2ndQuadrant.com> Date: Wed, 12 Dec 2012 05:44:24 +0400 Cc: =?iso-8859-1?Q?Niels_Kristian_Schj=F8dt?= , Jeff Janes , "pgsql-performance@postgresql.org" Message-Id: <3ADBD9A3-966F-40E8-AF78-0F2093D79BEE@gmail.com> 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> <50C7D7D2.4070605@2ndQuadrant.com> <2BCB6843-1396-42C9-A5BF-21C7C978FF4B@gmail.com> <50C7DDDE.1000000@2ndQuadrant.com> To: Craig Ringer X-Mailer: Apple Mail (2.1499) 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 --Apple-Mail=_8C3623BB-D898-4B1C-962C-99A01F59D02B Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 On Dec 12, 2012, at 5:29 AM, Craig Ringer wrote: > On 12/12/2012 09:17 AM, Evgeny Shishkin wrote: >>=20 >> Actually most of low-end SSDs don't do write caching, they do not = have enough ram for that. Sandforce for example. >>=20 > Or, worse, some of them do limited write caching but don't protect = their write cache from power loss. Instant data corruption! >=20 > I would be extremely reluctant to use low-end SSDs for a database = server. >=20 >> If we are talking about dedicated machine for database with ssd = drives, why would anybody don't by hardware raid for about 500-700$? > I'd want to consider whether the same money is better spent on faster, = higher quality SSDs with their own fast write caches. >=20 High quality ssd costs 5-7$ per GB. Consumer grade ssd - 1$. Highend - = 11$ New intel dc s3700 2-3$ per GB as far as i remember. So far, more than a year already, i bought consumer ssds with 300-400$ = hw raid. Cost effective and fast, may be not very safe, but so far so = good. All data protection measures from postgresql are on, of course. > --=20 > Craig Ringer http://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Training & Services --Apple-Mail=_8C3623BB-D898-4B1C-962C-99A01F59D02B Content-Transfer-Encoding: 7bit Content-Type: text/html; charset=windows-1252
On Dec 12, 2012, at 5:29 AM, Craig Ringer <craig@2ndQuadrant.com> wrote:

On 12/12/2012 09:17 AM, Evgeny Shishkin wrote:

Actually most of low-end SSDs don't do write caching, they do not have enough ram for that. Sandforce for example.

Or, worse, some of them do limited write caching but don't protect their write cache from power loss. Instant data corruption!

I would be extremely reluctant to use low-end SSDs for a database server.

If we are talking about dedicated machine for database with ssd drives, why would anybody don't by hardware raid for about 500-700$?
I'd want to consider whether the same money is better spent on faster, higher quality SSDs with their own fast write caches.


High quality ssd costs 5-7$ per GB. Consumer grade ssd - 1$. Highend - 11$
New intel dc s3700 2-3$ per GB as far as i remember.

So far, more than a year already, i bought consumer ssds with 300-400$ hw raid. Cost effective and fast, may be not very safe, but so far so good. All data protection measures from postgresql are on, of course.
-- 
 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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