[geeks] RAID0+1 and ideas, etc...

[Sandwich Maker]

" From: Jonathan Katz <jon at jonworld.com>
" 
" All,
" 
" Say you're running a Linux server. It has six Fusion IO cards, each
" presents two disk devices giving you a total of 12 disk devices. You
" want to RAID 1+0 this setup so that if any physical card or disk
" device dies, you're still operational.
" 
" My customer set this up using mdraid to stripe the two disk devices
" within the individual cards. So we go from 12 disk devices to six md
" stripes. Then the md stripes are mirrored card-by-card (so there are 3
" md mirror/RAID1 devices.) Then LVM is used to stripe the three
" remaining cards into one large volume that we use.
" 
" I'm not sure this is the best way to do it, and I want to hear from
" others who deal with this what they think (which is why I'm throwing
" this out there.) The requirement is for one decent sized, reliable
" storage pool of data. I think we have an extra layer of abstraction
" here, but I'm not sure how to redo this, or if we even should.
" 
" What say the mind trust?

what disksuite does in that situation is
a. mirror the drive pairs on each card
b. stripe the 6 mirrors
thus allowing you to survive any combination of 1-disk-per-card
failures.  it does this even if you try to configure 2 stripes and
mirror them, and it makes sense - with mirrored stripes, one failure
on each side would take you down.

i would mirror first, then lvm the mirrors.  it would make sense to
mirror pairs across cards, to provide card-failure hardness.
________________________________________________________________________
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