topic Changing number of disks in the root aggregate in ONTAP Discussions

Changing number of disks in the root aggregate

SkyMover — Wed, 04 Jun 2025 13:55:57 GMT

We have a system that is configured as follows:

FAS8020, DataONTAP : 8.3.2 P2 HDD size 2.0TB SATA

Name Node Type used% Available Used Total Volume Count Disk Count

System_A_aggr01 System_A Std 2 51.38TB 1.01TB 52.39TB 2 42

System_A_root System_A Std 32 2.83TB 1.32TB 4.15TB 1 5

System_B_aggr01 System_B Std 2 51.38TB 1.01TB 52.39TB 2 42

System_B_root System_B Std 32 2.83TB 1.32TB 4.15TB 1 5

Only 1 spare drive per system. All HDD used.

Client has decided they want to increase the number of spares by reducing the root aggregate from 5 to 3 HDD. There is one SVM defined and although there is only a small amount of data on it they would prefer to preserve that if possible.

What is the best way to achieve this? Worse case is trashing the system and rebuild it, but we'd prefer not to if we can avoid it

Is it possible to drop disks out of an aggregate providing there is sufficent remaining capacity to hold the data on the reduced number of disks?

My experience of DataONTAP is very limited so any guidance will be very much appreciated.

Many thanks

Chris

Re: Changing number of disks in the root aggregate

aborzenkov — Tue, 13 Mar 2018 11:09:42 GMT

There is no way to remove data disks from aggregate. It is possible to convert RAID_DP into RAID4 by removing one parity disk (but RAID4 is frowned upon today). Alternatively you can build new aggregate (it can use minimal number of disks initially, even 2, so you can utilize existing spares) and relocate root volume to this aggregate, then destroy original root aggergate. Relocating root volume is possible non-disruptively in your case (but see http://community.netapp.com/t5/Data-ONTAP-Discussions/Epsilon-and-root-move-from-an-aggregate-to-anoter/m-p/138789#M30619 for caveats).

Re: Changing number of disks in the root aggregate

SkyMover — Tue, 13 Mar 2018 12:08:08 GMT

Thanks for the swift reply. I'll review the procedure. If I used the two spares to make a new aggregate I guess you can simply add a 3rd disk later after the original root aggregate has been deleted and more drives become available?

Otherwise I would need to delete the data aggregate to release sufficient disks to make a new one. That isn't a major problem as the small amout of data that exists (<1GB) can easily be copied elsewhere.

Chris

Re: Changing number of disks in the root aggregate

aborzenkov — Tue, 13 Mar 2018 12:16:20 GMT

@SkyMover wrote:

I guess you can simply add a 3rd disk later after the original root aggregate has been deleted and more drives become available?

Correct. You can both go from RAID4 to RAID_DP as well as add more data disks.

Re: Changing number of disks in the root aggregate

GidonMarcus — Tue, 13 Mar 2018 15:10:48 GMT

one more thing.

if you do willing to re-initialize your system (both nodes) and upgrade to 9.2+, you can use ADP. and gain around 4.5TB more then the raid DP>RAID4 conversation (so around 8.5 TB saving in total from what you have now)..

https://kb.netapp.com/app/answers/answer_view/a_id/1030450

Gidi