From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Raid1 replaced with raid10? Date: Mon, 7 May 2007 16:58:44 +1000 Message-ID: <17982.52772.893500.146509@notabene.brown> References: <45FF1BDF.6060304@rabbit.us> <463B2D15.7020305@rabbit.us> <463B4C4F.9030504@tmr.com> <17982.42974.461499.127486@notabene.brown> <463ECBF5.7030206@rabbit.us> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Peter Rabbitson on Monday May 7 Sender: linux-raid-owner@vger.kernel.org To: Peter Rabbitson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Monday May 7, rabbit@rabbit.us wrote: > Neil Brown wrote: > > On Friday May 4, davidsen@tmr.com wrote: > >> Peter Rabbitson wrote: > >>> Hi, > >>> > >>> I asked this question back in march but received no answers, so here it > >>> goes again. Is it safe to replace raid1 with raid10 where the amount of > >>> disks is equal to the amount of far/near/offset copies? I understand it > >>> has the downside of not being a bit-by-bit mirror of a plain filesystem. > >>> Are there any other caveats? > >>> > > > > To answer the original question, I assume you mean "replace" as in > > "backup, create new array, then restore". > > You will get different performance characteristics. Whether they > > better suit your needs or not will depend largely on your needs. > > Hi Neil, > Yes I meant take an existing 2 drive raid1 array (non bootable data) and > put a raid10 array in its place. All my testing indicates that I get the > same write performance but nearly double the read speed (due to > interleaving I guess). It seemed to good to be true, thus I am asking > the question. Could you elaborate on your last sentence? Are there > downsides I could not think of? Thank you! I would have thought that you need "far" or "offset" to improve read performance, and they tend to hurt write performance (though I haven't really measured "offset" much). What layout are you using? NeilBrown