raidz/2 stripe widths

[Freddie Cash]

On Tue, Feb 16, 2010 at 11:47 AM, Peter C. Lai <peter at simons-rock.edu>wrote:

> Which one might be "better" on pool that will consist of 6 disks:
>
> 6x raidz2
>  or
> 2 stripes of 3 disks in raidz?
>
> It should provide slightly less reliability (still allows for 2 disks to be
> off the array at a time) but the latter should improve reads since a given
> read only has to touch 3 spindles at a time instead of 5?
>

Depends.  Do you want better reliability/redundancy (raidz2) or more
throughput/IOPS (2x raidz1)?

The max IOPS of a raidz vdev will be that of 1 disk.  Thus, to get better
IOPS, you have to have multiple raidz vdevs.

The overly-simplistic way to look at is to think of the entire raidz vdev as
a "single disk".  Then it's an easy comparison: 1 disk is slower than 2
disks striped together.
-- 
Freddie Cash
fjwcash at gmail.com