Le jeudi 28 juillet 2011 20:31:10 Doug Ledford, vous avez écrit : > On 07/20/2011 08:59 AM, brian.foster@xxxxxxx wrote: > >> -----Original Message----- > >> From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > >> owner@xxxxxxxxxxxxxxx] On Behalf Of Mike Power > >> Sent: Tuesday, July 19, 2011 3:14 PM > >> To: Roman Mamedov > >> Cc: linux-raid@xxxxxxxxxxxxxxx > >> Subject: Re: RAID 1 using SSD and 2 HDD > >> > >> Thanks for the link. That is the kind of thing I am looking for. > >> > >> On 07/19/2011 11:32 AM, Roman Mamedov wrote: > >>> On Tue, 19 Jul 2011 11:15:22 -0700 > >>> > >>> Mike Power<mpower@xxxxxxxxxxxx> wrote: > >>>> Is it possible to implement a RAID 1 array using two equal size HDD > >>>> and one smaller and faster SSD. The idea being that the resulting > >>>> RAID would have the same size of the HDD while picking up the speed > >>>> benefits of the SSD. > >>> > >>> See http://bcache.evilpiepirate.org/ > > > > Also, Roberto referred to the facebook flashcache implementation. It is > > based on device-mapper and last I tried bcache, probably a bit more > > production-worthy at the moment (though bcache looks intriguing long > > term, so I'd suggest to try both and draw your own conclusion): > > > > 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 how 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=internal --name=boot > /dev/sda1 --write-mostly --write-behind=128 /dev/sdb1 /dev/sdc1 > mdadm -C /dev/md/root -l1 -n3 -e1.2 --bitmap=internal --name=root > /dev/sda2 --write-mostly --write-behind=1024 /dev/sdb2 /dev/sdc2 > mdadm -C /dev/md/home -l1 -n2 -e1.2 --bitmap=internal --name=home > /dev/sdb3 /dev/sdc3 > mdadm -C /dev/md/repos -l1 -n3 -e1.2 --bitmap=internal --name=repos > /dev/sda4 --write-mostly --write-behind=1024 /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 blows > chunks some day. Obviously, if you need some other aspect of your home > directory to have the SSD benefit then modify to your tastes, but all my > scratch builds happen under ~/repos and the thing flies when compiling > stuff compared to how it used to be. One thing you didn't said is the respective size of the SSD and HD partitions. How did you determine them? Xavier xavier@xxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
