On 07/29/2011 01:50 PM, Xavier Brochard wrote:
Le vendredi 29 juillet 2011 11:32:02 John Robinson, vous avez écrit :
On 29/07/2011 00:53, Xavier Brochard wrote:
Le jeudi 28 juillet 2011 20:31:10 Doug Ledford, vous avez écrit :
On 07/20/2011 08:59 AM, brian.foster@xxxxxxx 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 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?
Since he's running RAID-1, the partitions on the SSD and HDDs must be
the same size. Note that the rest of the space on the HDDs was given to
/home and was not mirrored on the SSD.
Oh... I thought It was more like Mike's request:
"a RAID 1 array using two equal size HDD and one smaller and faster SSD"
Xavier
xavier@xxxxxxxxxxxxxx
It is. The SSD is 128GB and the two HDs are 500GB. The /home partition
does not exist on the SSD and it exactly equals the amount of space left
over on the two HDs after they have had matching partitions created to
duplicate the partitions on the SSD.
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