Re: raid10 layout for 2xSSDs

Kasper Sandberg [off-list ref] writes:

Hello.

I've been wanting to create a raid10 array of two SSDs, and I am
currently considering the layout.

As i understand it, near layout is similar to raid1, and will only
provide a speedup if theres 2 reads at the same time, not a single
sequential read.

so the choice is really between far and offset. As i see it, the
difference is, that offset tries to reduce the seeking for writing
compared to far, but that if you dont consider the seeking penalty,
average sequential write speed across the entire array should be roughly
the same with offset and far, with offset perhaps being a tad more
"stable", is this a correct assumption? if it is, that would mean offset
provides a higher "garantueed" speed than far, but with a lower maximum
speed.

mvh.
Kasper Sandberg

Doesn't offset have the copies of each stripe right next to each other
(just rotated). So writing one stripe would actualy write a 2 block
continous chunk per device.

With far copies the stripes are far from each other and you get 2
seperate continious chunks per device.

What I'm aiming at is that offset might better fit into erase blocks,
cause less internal fragmentation on the disk and give better wear
leveling. Might improve speed and lifetime. But that is just a
thought. Maybe test and do ask Intel (or other vendors) about it.

MfG
        Goswin