raidz2 a bit big

[Artis Caune]

2009/5/23 Randy Bush <randy at psg.com>:
> a dozen 2tb drives in a raidz2
>
> dfw1.psg.com:/root# zpool status
>  pool: tank
>  state: ONLINE
>  scrub: none requested
> config:
>
>        NAME        STATE     READ WRITE CKSUM
>        tank        ONLINE       0     0     0
>          raidz2    ONLINE       0     0     0
>            da0s3   ONLINE       0     0     0
>            da1s3   ONLINE       0     0     0
>            da2s1   ONLINE       0     0     0
>            da3s1   ONLINE       0     0     0
>            da4s1   ONLINE       0     0     0
>            da5s1   ONLINE       0     0     0
>            da6s1   ONLINE       0     0     0
>            da7s1   ONLINE       0     0     0
>            da8s1   ONLINE       0     0     0
>            da9s1   ONLINE       0     0     0
>            da10s1  ONLINE       0     0     0
>            da11s1  ONLINE       0     0     0


Reads on such configurations are very slow.

If one of your disk, for example, is capable of 100 IO per/sec, then:
with 12 disks in one raidz2 vdev you get only 100 IOPS
with 4 disks in raidz2 (total 3 raidz2 vdevs) you get 300 IOPS
with 2 disks in mirror (total 6 mirror vdevs) you can get 1200 IOPS




-- 
Artis Caune

    Everything should be made as simple as possible, but not simpler.