CDOT Raid Groups

A cool bit of trivia about expanding RAID Group sizes.  

For the command storage aggregate modify

For the command storage aggregate add-disks(both quotes from 8.2 command manual)

Which means if you need to balance an unusual number of disks today but will add more disks at some future date, if you want to have small RG’s now and expand them in the future you have to be careful.  For example, if you have 45 disks and want a RG size today of 15 but 20 later, you’d do this:

Storage aggr create –aggregate aggr1 -diskcount 15 –disktype SAS –maxraidsize –s 20

Storage aggr add-disks –aggregate aggr1  -diskcount 15 -disktype SAS –raidgroup –g new

Storage aggr add-disks –aggregate aggr1 -diskcount 15 -disktype SAS –raidgroup –g new

But then we found this:

(Clustered Data ONTAP 82 Physical Storage.pdf)

While this excerpt doesn’t explicitly state you can, I tested in the lab and confirmed: you can manually expand RG sizes of all the RG’s in the aggregate by modifying the max RG size then manually adding disks to each RAID Group.

Storage aggregate add-disks –aggregate aggr1 -diskcount 5 -disktype SAS –raidgroup rg0

NetApp Training Brain Dump: Experimenting

Quick notes on things I tested today:

• If you run a disk fail command, you will have to wait a few hours for the data on that disk to be copied to a spare.
• There is a -i trigger for the disk fail command that will immediately fail the disk, without copying the data.
• If you have no spares and you have a disk that is not assigned and is not in use, you have to assign that disk to the controller before it will be used as a spare.  If you have options disk.auto_assign on, it will have already been assigned to a controller.  In either case, you won't need to add the disk to an aggregate: the system detects it as a spare and grabs it in the place of the failed disk.
• To see how many failed disks you have, use vol status -f
• To see how many spares you have, use vol status -s
• If you want to see the status of your disks, disk show won't do it.  You'll need to use disk show -v to see failed disks, and neither will show spare disks as being spare.  
• You can't resize an aggregate's RAID roups.  You can however use aggr options raidsize to set the size for new RAID Groups that are created for this aggregate.