ONTAP Hardware

Disk Config - 2040HA + DS4324


I have a configuration as follows – I want to maximise capacity without sacrificing performance:

1 x 2040HA – 12 x 300GB 15k

1 x DS4342 – 24 x 300GB 15k

I was thinking of splitting the disks 50/50 and having 18 per controller; however, I do not want to have 2 spares per controller – Can I increase RG0 to 17 disks (15 D + 2 P) or is it a bad idea to deviate from the recommended for just 1 disk? – Also, what about 12 for one controller and 24 for the other, increasing the RG on controller 2 to 23 (1 S, 2 P, 20 D)???

Just looking for some advice and ideas?



In your case 1 spare per controller is fine.

How to divide your disks is ultimately up to you. I.e. 12/24 if you need more performance/capacity on the other controller.

If you ever need to upgrade the 2040 to a 32xx system, you can't reuse the internal disks, in which case 12/24 is easier to migrate.

You can increase the size of the raidgroup to 17 (max is 28).

Do this before adding disks, or else ontap will try to create a 2nd raidgroup, in which case you will end up with uneven RG's.




Will increasing the RG by a mere one disk have any negative impact?

Also, if you buy a 2040HA both root vols will be located within the unit - If at a later date you buy a 4324 can you move the root vol of one controller to the tray so you can have a 12/24 split?



Here is a very informative thread about RG sizes:


Bigger RG size yields more usable capacity, but means longer rebuild times in a case of a disk failure.

This leads us back to the 1 vs. 2 hot-spares dilemma:

- 1 hot-spare means (obviously) more capacity

- 2 hot-spares are required to enable Maintenance Center:

"If Data ONTAP drive health monitoring determines that a drive has surpassed an error threshold, rapid RAID recovery is initiated to a hot spare. [...] Maintenance Center requires that at least two hot spares are present in the system. NetApp recommends using Maintenance Center to provide additional intelligence for drive error discovery and correction."