From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: RAID 1 using SSD and 2 HDD Date: Fri, 29 Jul 2011 10:32:02 +0100 Message-ID: <4E327E12.30900@anonymous.org.uk> References: <4E25C9BA.1060401@dodtsair.com> <24EACA6AC4B506428C92FE7C172FEF4E02084CF0@MX16A.corp.emc.com> <4E31AAEE.30601@redhat.com> <201107290153.45227.xavier@alternatif.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <201107290153.45227.xavier@alternatif.org> Sender: linux-raid-owner@vger.kernel.org To: Xavier Brochard Cc: Doug Ledford , brian.foster@emc.com, mpower@dodtsair.com, rm@romanrm.ru, linux-raid@vger.kernel.org List-Id: linux-raid.ids On 29/07/2011 00:53, Xavier Brochard wrote: > Le jeudi 28 juillet 2011 20:31:10 Doug Ledford, vous avez =E9crit : >> On 07/20/2011 08:59 AM, brian.foster@emc.com wrote: [...] >>>> On 07/19/2011 11:32 AM, Roman Mamedov wrote: [...] >>>>> See http://bcache.evilpiepirate.org/ [...] >>> https://github.com/facebook/flashcache >> >> Having not looked at those two, I can say that an md raid1 with two = hard >> drives and one SSD works *very* well. It's blazing fast. Here's ho= w I >> set mine up: >> >> SSD: three partitions, one for boot, one for /, and one for ~/repos >> (which is where all my git/cvs/etc. checkouts reside) >> hard disks: four partitions, one for boot, one for /, one for /home,= one >> for ~/repos >> >> Then I created four raid1 arrays like so: >> >> mdadm -C /dev/md/boot -l1 -n3 -e1.0 --bitmap=3Dinternal --name=3Dboo= t >> /dev/sda1 --write-mostly --write-behind=3D128 /dev/sdb1 /dev/sdc1 >> mdadm -C /dev/md/root -l1 -n3 -e1.2 --bitmap=3Dinternal --name=3Droo= t >> /dev/sda2 --write-mostly --write-behind=3D1024 /dev/sdb2 /dev/sdc2 >> mdadm -C /dev/md/home -l1 -n2 -e1.2 --bitmap=3Dinternal --name=3Dhom= e >> /dev/sdb3 /dev/sdc3 >> mdadm -C /dev/md/repos -l1 -n3 -e1.2 --bitmap=3Dinternal --name=3Dre= pos >> /dev/sda4 --write-mostly --write-behind=3D1024 /dev/sdb4 /dev/sdc4 >> >> Works for me with stellar performance. Treats the SSD as the only >> device that matters on the three arrays it participates in with the = hard >> drives there merely as a backing store for safety in case the SSD bl= ows >> chunks some day. Obviously, if you need some other aspect of your h= ome >> directory to have the SSD benefit then modify to your tastes, but al= l my >> scratch builds happen under ~/repos and the thing flies when compili= ng >> stuff compared to how it used to be. > > One thing you didn't said is the respective size of the SSD and HD pa= rtitions. > How did you determine them? Since he's running RAID-1, the partitions on the SSD and HDDs must be=20 the same size. Note that the rest of the space on the HDDs was given to= =20 /home and was not mirrored on the SSD. 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