From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Nelson Subject: Re: Ideal hardware spec? Date: Sun, 26 Aug 2012 08:29:40 -0500 Message-ID: <503A24C4.5060807@inktank.com> References: <20120822135530.GB10015@csail.mit.edu> <5034E9F3.10001@widodh.nl> <20120822154615.GF10015@csail.mit.edu> <5035FF18.3030209@widodh.nl> <503A056E.2020804@widodh.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:45895 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751457Ab2HZN3p (ORCPT ); Sun, 26 Aug 2012 09:29:45 -0400 Received: by ialo24 with SMTP id o24so6399770ial.19 for ; Sun, 26 Aug 2012 06:29:45 -0700 (PDT) In-Reply-To: <503A056E.2020804@widodh.nl> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Wido den Hollander Cc: Andrey Korolyov , "ceph-devel@vger.kernel.org" On 08/26/2012 06:15 AM, Wido den Hollander wrote: > CC'ing this one back to the list. > > On 08/25/2012 09:58 PM, Andrey Korolyov wrote: >>> >>> They should be much more reliable than regular USB sticks due to >>> their SLC >>> memory. >>> >>> You could also take a look at these: >>> http://www.transcend-info.com/industry/products_details.asp?CatNo=2&SerNo=14&ModNo=28&Func1No=1 >>> >>> >>> >> >> Did you tried yet those or simular sticks for CEPH journal? Right now >> I am using Intel 313`s, which is very fast and have durability/price >> ratio a far higher than any imaginable MLC, but they occupying one HDD >> slot which is a quite impractical. >> > > No, I haven't tried, but I think it won't work. > > These kind of SLC chips don't do random writes that great, you'll > probably get something like 4MB/sec in random writes. > > Bigger SSDs have more cells to spread the writes over, those small > sticks don't. > > The Intel 3XX or 5XX serie should work just fine for journaling, I'd > however recommend you change the Host Protected Area to ~50% of the > available capacity to prevent write-degradation over time. > > Wido > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Not just write degradation, but undersubscribing the SSDs should hopefully help them last a little longer under such a heavy write workload. We are doing 3 10GB journals per 180GB Intel 520 on our supermicro test node. Mark