RAID 1 on top of RAID 0

[pk]

What would the outcome be of a RAID controller creating a RAID 0 array
and then someone creating a software RAID 1 on top of it? It sounds
extremely messed up and unfortunately I believe I've just inherited
this. Is there any way to just create a hardware RAID 1 out of this,
or is it not as bad as I think it is?

Thanks.

pk

 

[Bob Willard]

What would the outcome be of a RAID controller creating a RAID 0 array
and then someone creating a software RAID 1 on top of it? It sounds
extremely messed up and unfortunately I believe I've just inherited
this. Is there any way to just create a hardware RAID 1 out of this,
or is it not as bad as I think it is?

Thanks.

pk

That is a pretty standard arrangement. In simplest form, use 4 HDs, then
create a pair of RAID0 arrays, then create a RAID1 array whose members
are the two RAID0 arrays. This gives you high performance (from striping
with RAID0) and reliability (from mirroring with RAID1).

 

[pk]

Hmm, I should have been clearer. There are only 2 hard drives in this
setup. I don't have any sort of redundancy or speed increase, do I?
I'm having trouble visualizing it.

 

[Bob Willard]

Hmm, I should have been clearer. There are only 2 hard drives in this
setup. I don't have any sort of redundancy or speed increase, do I?
I'm having trouble visualizing it.

Not enough info to tell, but you sure aren't getting all the benefits I listed
in my note on normal RAID1 on RAID0, since that requires at least 4 HDs.

If both HDs are members of a RAID0 array, then RAID1 on top of that is a waste
and probably causes a tiny bit of lost performance. If each HD is the only
member of a RAID0 array, then the RAID0 is a waste (i.e., no performance gain),
but RAID1 still gets you data integrity via redundancy.