From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Tran Subject: Re: EVMS or md? Date: Mon, 04 Apr 2005 14:28:48 -0500 Message-ID: <1112642928.25469.28.camel@dyn95395156> References: <200504040708.j3478bm03863@www.watkins-home.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200504040708.j3478bm03863@www.watkins-home.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi Guy, On Mon, 2005-04-04 at 02:08, Guy wrote: > I am top posting since I am starting a new topic. > > Don't get me wrong, I like and trust md, at least with kernel 2.4. > > This is the first I knew about EVMS, the website makes it sound wonderfull! > http://evms.sourceforge.net/ > > Is EVMS "better" than md? > Is EVMS replacing md? > Any performance data comparing the 2? EVMS uses MD and Device Mapper (DM). So, EVMS does not replace MD. For RAID-1 & RAID-5, EVMS ioctl md driver to start the array. For MD's RAID-0 and LINEAR arrays, EVMS uses DM stripe and linear targets to create device nodes. You can say EVMS replaces mdadm (sorry, NeilB :)) Regarding performance issue (raid1 & raid5), I/O requests from MD will appear on DM's queue. So, it is probably slower. How much slower, we never run any benchmark to find out. > > One bad point for EVMS, no RAID6. :( We (EVMS team) intended to support RAID6 last year. But as we all remember RAID6 was not stable then. I may write a plugin to support RAID6 soon. > One good point for EVMS, bad Block Relocation (but only on writes). > Not sure how EVMS handles read errors. As I mentioned above, kernel MD driver handle I/O requests for raid1 and raid5. > > I am getting on the mailing list(s). I must know more about this!!! > Welcome aboard :) -- Regards, Mike T.