Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1UGFqi-0003sH-V4 for pgsql-performance@arkaria.postgresql.org; Thu, 14 Mar 2013 21:38:09 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.72) (envelope-from ) id 1UGFqi-0002RV-EL for pgsql-performance@arkaria.postgresql.org; Thu, 14 Mar 2013 21:38:08 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1UGFqg-0002RN-DU for pgsql-performance@postgresql.org; Thu, 14 Mar 2013 21:38:06 +0000 Received: from [2404:130:0:10::40:2] (helo=mail.catalyst.net.nz) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1UGFqd-0005Lv-FN for pgsql-performance@postgresql.org; Thu, 14 Mar 2013 21:38:06 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.catalyst.net.nz (Postfix) with ESMTP id 006C033449; Fri, 15 Mar 2013 10:37:57 +1300 (NZDT) X-Virus-Scanned: Debian amavisd-new at catalyst.net.nz Received: from mail.catalyst.net.nz ([127.0.0.1]) by localhost (bertrand.catalyst.net.nz [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9M6ioA-VC6Y5; Fri, 15 Mar 2013 10:37:55 +1300 (NZDT) Received: from [IPv6:2404:130:0:1000:55a5:da7a:9b0c:d352] (unknown [IPv6:2404:130:0:1000:55a5:da7a:9b0c:d352]) (Authenticated sender: mark.kirkwood) by mail.catalyst.net.nz (Postfix) with ESMTPSA id C739F32EBA; Fri, 15 Mar 2013 10:37:55 +1300 (NZDT) Message-ID: <51424333.608@catalyst.net.nz> Date: Fri, 15 Mar 2013 10:37:55 +1300 From: Mark Kirkwood User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130221 Thunderbird/17.0.3 MIME-Version: 1.0 To: Bruce Momjian CC: Gregg Jaskiewicz , Greg Smith , postgres performance list , =?ISO-8859-1?Q?Niels_Kristian_Schj=F8dt?= Subject: Re: New server setup References: <4D6D1410-2208-4DAA-BD64-69BE1FD94E55@autouncle.com> <513CADB7.4030803@2ndQuadrant.com> <20130314185424.GA28770@momjian.us> In-Reply-To: <20130314185424.GA28770@momjian.us> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2404:130:0:10::40:2 (failed) X-Pg-Spam-Score: -1.1 (-) 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 On 15/03/13 07:54, Bruce Momjian wrote: > Only use SSDs with a BBU cache, and don't set SSD caches to > write-through because an SSD needs to cache the write to avoid wearing > out the chips early, see: > > http://momjian.us/main/blogs/pgblog/2012.html#August_3_2012 > I not convinced about the need for BBU with SSD - you *can* use them without one, just need to make sure about suitable longevity and also the presence of (proven) power off protection (as discussed previously). It is worth noting that using unproven or SSD known to be lacking power off protection with a BBU will *not* save you from massive corruption (or device failure) upon unexpected power loss. Also, in terms of performance, the faster PCIe SSD do about as well by themselves as connected to a RAID card with BBU. In fact they will do better in some cases (the faster SSD can get close to the max IOPS many RAID cards can handle...so more than a couple of 'em plugged into one card will be throttled by its limitations). Cheers Mark -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance