From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Majed B." Subject: Re: Full use of varying drive sizes? Date: Tue, 22 Sep 2009 16:07:53 +0300 Message-ID: <70ed7c3e0909220607y692e15a2s64aac9bd729422ef@mail.gmail.com> References: <697034.10751.qm@web51302.mail.re2.yahoo.com> <73e903670909220452r2c4098c5w321f65c103b68a83@mail.gmail.com> <4AB8C9D9.6060406@anonymous.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4AB8C9D9.6060406@anonymous.org.uk> Sender: linux-raid-owner@vger.kernel.org To: Linux RAID List-Id: linux-raid.ids When I first put up a storage box, it was built out of 4x 500GB disks, later on, I expanded to 1TB disks. What I did was partition the 1TB disks into 2x 500GB partitions, then create 2 RAID arrays: Each array out of partitions: md0: sda1, sdb1, sdc1, ...etc. md1: sda2, sdb2, sdc2, ...etc. All of those below LVM. This worked for a while, but when more 1TB disks started making way into the array, performance dropped because the disk had to read from 2 partitions on the same disk, and even worse: When a disk fail, both arrays were affected, and things only got nastier and worse with time. I would not recommend that you create arrays of partitions that rely on each other. I do find the JBOD -> Mirror approach suggested earlier to be convenien= t though. On Tue, Sep 22, 2009 at 3:58 PM, John Robinson wrote: > On 22/09/2009 12:52, Kristleifur Da=C4=91ason wrote: >> >> On Tue, Sep 22, 2009 at 11:24 AM, Jon Hardcastle >> wrote: >>> >>> Hey guys, >>> >>> I have an array made of many drive sizes ranging from 500GB to 1TB = and I >>> appreciate that the array can only be a multiple of the smallest - = I use the >>> differing sizes as i just buy the best value drive at the time and = hope that >>> as i phase out the old drives I can '--grow' the array. That is all= fine and >>> dandy. >>> >>> But could someone tell me, did I dream that there might one day be >>> support to allow you to actually use that unused space in the array= ? Because >>> that would be awesome! (if a little hairy re: spare drives - have t= o be the >>> size of the largest drive in the array atleast..?) I have 3x500GB 2= x750GB >>> 1x1TB so I have 1TB of completely unused space! >> >> Here's a thought: >> Imaginary case: Say you have a 500, a 1000 and a 1500 GB drive. You >> could JBOD the 500 and the 1000 together and mirror that against the >> 1500GB. >> >> Disclaimer: >> I don't know if it makes any sense to do this. I haven't seen this >> method mentioned before, IIRC. It may be too esoteric to get any >> press, or it may be simply stupid. > > Sure you can do that. In Jon's case, a RAID-5 across all 6 discs usin= g the > first 500GB, leaving 2 x 250GB and 1x 500GB free. The 2 x 250GB could= be > JBOD'ed together and mirrored against the 500GB, giving another 500GB= of > usable storage. The two md arrays can in turn be JBOD'ed or perhaps b= etter > LVM'ed together. > > Another approach would be to have another RAID-5 across the 3 larger = drives, > again providing an additional 500GB of usable storage, this time leav= ing 1 x > 250GB wasted, but available if another 1TB drive was added. I think t= his may > be the approach Netgear's X-RAID 2 takes to using mixed-size discs: > http://www.readynas.com/?p=3D656 > > Cheers, > > John. > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid"= in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info.ht= ml > --=20 Majed B. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html