You can always go with a larger RAID group size - it does support up to 28.  However, at some point you have to bite the bullet and lose 2 more disks to parity.  It depends on how you want the math to work out in the long run.

The reason you want to add the disks in large sets is so you have a more level writing of the data to the disks - you don't want to get 3-4 'hot disks' slowing the whole aggregate down until the data is spread evenly among the aggregate.'s new disks...

-----Original Message-----
From:   owner-toasters@mathworks.com on behalf of Sphar, Mike
Sent:   Mon 3/19/2007 11:06 AM
To:     toasters@mathworks.com
Cc:    
Subject:        RE: FAS3020 - aggr best practises.

Point one reminds me of a question I've been pondering.  I've got a
filer using RAID-DP with 3X14-disk raid groups, and currently 7 spares.
Ideally I'd only keep two spares, but I'm still not clear on the
pros/cons of adding a 5 disk raid group, effectively only adding three
more data disks to the volume.



I'm not in a space crunch currently but I certainly will be at some
point.  Is it best to leave so many extra spares until I can add a full
raid group all at once?  Or in my case is it not that important?





--

Michael W. Sphar - IS&T - Lead Systems Administrator

SMBU Engineering Support Services, BMC Software



________________________________

From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com]
On Behalf Of Learmonth, Peter
Sent: Saturday, March 17, 2007 6:43 PM
To: Darish Rajanayagam; toasters@mathworks.com
Subject: RE: FAS3020 - aggr best practises.



Hi Darish

Welcome to NetApp and to Toasters!



1.  You can do an "aggr add aggr0 56" or use the FilerView GUI and add
all 56 of the new disks into the existing aggregate.  You can physically
add the shelves and add them to the aggr while the filer is up and
running.  I see no disadvantages, and that is the best practice.  (Add
disks in large sets, ideally the raid group size).