----- Original Message ----- From: "kevin graham" kgraham@dotnetdotcom.org To: "Corris Randall" corris@acc.am.ericsson.se Cc: toasters@mathworks.com Sent: Tuesday, July 11, 2000 11:13 AM Subject: Re: volume/shelf containment
what you (Douglas) could do is buy a bigger drive (36GB if you have 18's) and plop that in as a spare, then leave only one 18GB spare and
the
36GB spare and it should build on the 18GB first (if the rest of your disks are 18 of course) then if you have another loss, it'll use the
36GB.
Unless the failed disk is the parity, in which case the 36gb will be used.
Why would it do that, when the parity is only 36GB? We're talking about what to do during a failure, not adding a new disk. If it fails over to the 36GB drive when an 18 is available, I would consider that a bug.
Putting only 1 of a larger disk is always a dangerous thing, as you're essentially running w/o a spare.
I don't follow what you mean here. He's talking about only one 36GB drive and having it be a "second spare". (Presumably this is safer than having only one global spare available, since you want it to use the 36GB in case the other raid group fails before you can replace it.) Of course, the other volume could still fail and build on the 18GB disk on the other shelf.
Further, if you rebuild a 18 onto a 36, you _don't_ get a bigger volume -- you get a more expensive 18gb disk (which you'd probably have to relabel to get the filer to use all 36gb of again).
AFAIK, you don't have to relabel to do this, although you would need to go through a raid fail to replace it with an 18.
Some features to support rolling upgrades of disks would be damn smooth though. (proactively fail a disk onto a bigger one, which grows the volume and rebuilds).. Makes an upgrade path to $BIGDISK[$#BIGDISK+1] quite attractive.
That's already supported for the parity drive (so you can add bigger disks in the first place) but doing it for a data drive would be a little trickier. (If you had a situation where the smaller parity failed and *only* a bigger drive is available, it would be nice if it did this too, per your concern in the first paragraph... I don't know if the filer actually does this, though?)
Bruce