From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aryeh Gregor Subject: Re: SSD & mechanical disc in RAID 1 Date: Tue, 2 Feb 2010 09:07:31 -0500 Message-ID: <7c2a12e21002020607j38d35a1bq85d37221b922da0f@mail.gmail.com> References: <7a329d911001090953j17829cd9qca0888fbcd7b4805@mail.gmail.com> <72dbd3151002011310g57fa9b66j2798aa0acde199b2@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <72dbd3151002011310g57fa9b66j2798aa0acde199b2@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: David Rees Cc: Wil Reichert , linux raid List-Id: linux-raid.ids On Mon, Feb 1, 2010 at 4:10 PM, David Rees wrote: > I suspect that if you used write-behind with a write-intent bitmap > stored only on the SSD, you'd get some of that performance back, but > potentially lose a bit of reliability. You'd only lose data here if the SSD died and the machine crashed *at the same time*, right? Doesn't seem like a big deal to me -- if the events are even a minute or two apart, you'd be fine (right?). By contrast, if I understand correctly, you can get data corruption in RAID5 if you lose a disk and then the machine crashes *any* time before a new disk is resynced.