From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: Full use of varying drive sizes? Date: Tue, 22 Sep 2009 13:58:01 +0100 Message-ID: <4AB8C9D9.6060406@anonymous.org.uk> References: <697034.10751.qm@web51302.mail.re2.yahoo.com> <73e903670909220452r2c4098c5w321f65c103b68a83@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <73e903670909220452r2c4098c5w321f65c103b68a83@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Linux RAID List-Id: linux-raid.ids On 22/09/2009 12:52, Kristleifur Da=F0ason 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 a= nd 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 ti= me and hope that as i phase out the old drives I can '--grow' the array= =2E That is all fine and dandy. >> >> But could someone tell me, did I dream that there might one day be s= upport to allow you to actually use that unused space in the array? Bec= ause that would be awesome! (if a little hairy re: spare drives - have = to be the size of the largest drive in the array atleast..?) I have 3x5= 00GB 2x750GB 1x1TB so I have 1TB of completely unused space! >=20 > 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. >=20 > 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 using=20 the first 500GB, leaving 2 x 250GB and 1x 500GB free. The 2 x 250GB=20 could be JBOD'ed together and mirrored against the 500GB, giving anothe= r=20 500GB of usable storage. The two md arrays can in turn be JBOD'ed or=20 perhaps better LVM'ed together. Another approach would be to have another RAID-5 across the 3 larger=20 drives, again providing an additional 500GB of usable storage, this tim= e=20 leaving 1 x 250GB wasted, but available if another 1TB drive was added.= =20 I think this may be the approach Netgear's X-RAID 2 takes to using=20 mixed-size discs: http://www.readynas.com/?p=3D656 Cheers, John. -- 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