On Mon, 9 Oct 2000, Bruce Sterling Woodcock wrote:
----- Original Message ----- From: "Steve Losen" scl@sasha.acc.virginia.edu
If you have a raid group of 18GB drives, and add a 36GB drive, the 36GB drive becomes the new parity drive. The old 18GB parity drive becomes a data drive, giving you 18GB of space. After that, all 36GB drives you add give you the full 36GB of space.
(Caveat: This is how Netapp's RAID 4 works. With other vendors, YMMV.)
Bruce
Beware that if an 18G drive fails and the only available hot spare is a 36G drive, then only 18G of the 36G spare drive is used and 18G is wasted. This situation is permanent until the volume is destroyed, at least under DOT 5.3.x.
I thought you could, if you wanted to, get a new 18G drive, fail the 36G drive, and replace it with an 18G drive and the software was smart enough to reconstruct. But, I could be wrong, and of course you put yourself at risk and reduced performance during the reconstruction.
Ooooo...crap. Could someone from NetApp please officially comment on the expected behaviour?
I've got a filer with a shelf of 36's (one RG/volume) and two shelves of 18's (one RG/volume); each RG has a hot spare. What I do NOT want to happen is the situation described in this thread--an 18 GB disk dying, ONTAP taking the 36 GB drive in as the new parity drive, and my not being able to fail it out because it is now a *full* 36 GB parity drive, instead of an 18 GB parity and 18 GB wasted.
An answer of "upgrade your old drives" is not acceptable. ;)
Until next time...
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