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).
 
2.  Rebuild times vary depending on load.  You can adjust the priority.  This is less of an issue on a filer using RAID-DP, because you are still protected if you lose a second disk in the same raid group.  Having one hot spare for this number of disks is fine, again since you have RAID-DP.  Some people may have different opinions.
 
3.  Even if you do nothing, WAFL will spread writes across all spindles, even for existing volumes.  You can also reallocate, but much of that will just happen over time.  Reallocate will usually help with reads.
 
Feel free to ask your questions here, but you should also be able to get these answered from your NetApp or partner SE - that's what we get paid for!
 
Share and enjoy!
 
Peter

From: Darish Rajanayagam [mailto:darishr@softcom.biz]
Sent: Saturday, March 17, 2007 9:59 AM
To: 'toasters@mathworks.com'
Subject: FAS3020 - aggr best practises.

Greetings:
 
I am new to the NetApp world and am looking for some advice/guidance. We  purchased a NetApp 3020i with two shelves (10K 144GB FC drives) a few months ago. We have now placed an order for 4 additional shelves (fully loaded) with 10K 144GB drives.
 
The current configuration is one large RAID DP Group with 1 HotSpare (27 Disk DP RAID Group), which belong to one aggregate (aggr0).
 
My question:
 
  1. The new enclosures, should I create 2 x 28 Disk DP RAID groups and add it to the existing aggregate? The application we run is IO intensive and more spindles the better. Does anyone see any disadvantages of doing the above?
  2. Does anyone have a formula to calculate mean time to Repair on the 10K 144GB disks on a busy filer? I only have one hot spare disk, should I add more, is there a rule of thumb?
  3. We currently have multiple volumes on the filer, after adding the new shelves/spindles, if I run a reallocate  on the existing volumes, would it take advantage of the additional spindles.
 
Any help/guidance greatly appreciated.
 
Thanks,
Darish.