From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pigeon.gentoo.org ([208.92.234.80] helo=lists.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.77) (envelope-from ) id 1Sp0t4-0007v0-7J for garchives@archives.gentoo.org; Wed, 11 Jul 2012 17:39:42 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id C38EAE0683; Wed, 11 Jul 2012 17:39:21 +0000 (UTC) Received: from mail-qa0-f53.google.com (mail-qa0-f53.google.com [209.85.216.53]) by pigeon.gentoo.org (Postfix) with ESMTP id 72D2FE04E7 for ; Wed, 11 Jul 2012 17:37:38 +0000 (UTC) Received: by qaas11 with SMTP id s11so1149213qaa.19 for ; Wed, 11 Jul 2012 10:37:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=2e13Y+OZ7I8xYfliL8UFN8Tr07ROgJC0qWhtPo4wIzI=; b=bvLmJ2u4At9S1yFFwsmAchDAf0lJ66hazUfb776bnC3kKEd0lT38nsW2JBkyCS6u/E a5xhtFDD+dBC2CKcdEDOsrbmyd7iIY0pRcOtm18jgfgimSRaak9eo/dvkr33/7drKQkz FCpa/Deh0aHNWdfn/ejzW7SNboGuhcXh/XMg5HBT5Ij1O/1iKd5OfO6WlNr58r3R9n4c Ew5cBaBJEVMRXKlxLKcR7ZqrRvXgiyvKo6QfY90D4x2ZNkwke4giuXpr4wXle/OhpqPz buwGJdXyecK31t3oMp0GYT7I3cVyzEE6uXZXipyyng6i+XdlbYzZBjSoCJknaSVEZZJq rLMQ== Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Received: by 10.229.135.146 with SMTP id n18mr12489580qct.138.1342028257957; Wed, 11 Jul 2012 10:37:37 -0700 (PDT) Received: by 10.229.190.196 with HTTP; Wed, 11 Jul 2012 10:37:37 -0700 (PDT) In-Reply-To: <4FFB1443.4090500@gmail.com> References: <4FFB1443.4090500@gmail.com> Date: Wed, 11 Jul 2012 10:37:37 -0700 Message-ID: Subject: Re: [gentoo-user] OT: HW-raid1 & SSD? From: Mark Knecht To: gentoo-user@lists.gentoo.org Content-Type: text/plain; charset=UTF-8 X-Archives-Salt: 5abad854-b51c-4fa5-a4fa-ba88c532f23e X-Archives-Hash: 232d4bdf308d9570f002e69bcbb0c03f On Mon, Jul 9, 2012 at 10:26 AM, Jarry wrote: > Hi, > > I'm building small server for VPS-hosting purpose (not decided > yet, probably KVM or ESXi). Althought it is "non production", > reliability is still issue for me. I'm considering using two > small SSD (ie. Intel 313, 24GB, SLC) in hw-raid1 (Adaptec 3805) > just for hypervisor, and 2xHDD/raid1 for VPS. > > I started looking for info on internet but results are not > conclusive. Opinions vary from "no problem, use SSD&raid1" > to "using SSD in raid is not recommended no matter if it is > SW or HW". Mostly missing trim-command is mentioned as reason > for not using SSD in any raid. > > Does anyone have any experience with SSD in raid (SW or HW)? > Is it safe to use it on server? > > Jarry On the surface it doesn't make a lot of sense to me. If you have two drives mapped against each other in a RAID-1, and then you TRIM part of 1 drive but don't TRIM the same part of the 2nd drive, it seems to me that you're discarding part of your redundancy, aren't you? What would mdadm itself (or anything else) know about remapping that stuff? Granted, mdadm could be informed and probably reconstruct the RAID-1 in a new location, but as you TRIM out different parts of each SSD it's going to get messy I think. If you look up TRIM in Wikipedia there's a little bit of info suggesting some support for some file systems. http://en.wikipedia.org/wiki/TRIM I can say from reading the mdadm list for the last year that it's a conversation that doesn't come up all that often and mostly goes away pretty fast most of the time there. Check their archives. In my case I'm running a small server here that's currently running 3 VMs which is typical for my work day. I'm considering adding a single SSD to the system to host the VMs but using rsync to back them up to HDD RAID each evening. HTH, Mark