topic How to get the most usable space having a few disks in FAS system? in ONTAP Hardware

How to get the most usable space having a few disks in FAS system?

danaskazlauskas — Thu, 05 Jun 2025 06:59:50 GMT

Hi,

I have FAS2020 (2 x node) with 12 SAS disks. I will appreciate any suggestions helping me to use these 12 disks in most effective way considering usable space.

The main thing is - is it possible to use 6 disks where Data ONTAP is installed? For example, create volumes for data in these two aggregates, o just extend aggregate there Data ONTAP is located and use single aggregate (for one filer) for both Data ONTAP and data?

If I configure system leaving default values I get only 4 disks for data (6 disks - Data ONTAP, 2 disks - spares).

TIA.

BR,

Danas

Re: How to get the most usable space having a few disks in FAS system?

edriel — Fri, 18 Feb 2011 11:28:25 GMT

Hello Danas,

There are multiple ways to do this. Minimum you need 1 parity (raid 4 aggregates), 1 spare and 1 data disk on each controller. After this you have 6 disks available. You can add these disks on one node to create an aggregate as big as possible and use the other node only for cluster failover (and only use 1 CPU for all the data).

Another possibility is add 3 disks to each node. With this setup you can use performance of both node CPU's.

Regards,

Eelco

Re: How to get the most usable space having a few disks in FAS system?

vmsjaak13 — Fri, 18 Feb 2011 12:12:36 GMT

Several options:

Four data disks per controller: pro: utilize CPU/RAM resources of both controllers, cons: usable space per controller. No hot spares.

C1: 6 disks (4D + 2P) (no hotspare)

C2: 6 disks (4D + 2P) (no hotspare)

Eight data disks on controller 1: pro: maximize space on 1 controller, use 2nd only for cluster failover. cons: CPU/RAM resources of 1 controller. Other isn't doing anything. No hot spares

C1: 10 disks (8D + 2P) 0 HS

C2: 2 disks (RAID4: 1D + 1P) 0 HS

Seven data disks. Same as previous, but with an hot spare for controller 1

C1: 10 disks (7D + 2P) 1 HS

C2: 2 disks (RAID4: 1D + 1P) 0 HS

There are probably other options. All depends on your needs.

What you've certainly noticed is, that if you're willing to work without spares (but still use RAID-DP), you end up with 8 data disks.

Mind you some of these scenario's go against NetApp best practises, but in this case, FAS2020A with 12 disks you gotta be creative.

Regards,

Niek

Re: How to get the most usable space having a few disks in FAS system?

danaskazlauskas — Fri, 18 Feb 2011 12:20:42 GMT

Does your answer imply, that I can use the same aggregate for for Data ONTAP OS and customer's data?

Thanks.

BR,

Danas

Re: How to get the most usable space having a few disks in FAS system?

vmsjaak13 — Fri, 18 Feb 2011 12:22:25 GMT

Yes.

On small FAS systems there's no point having a seperate root aggregate. It simply costs too much disks.

Regards,

Niek

Re: How to get the most usable space having a few disks in FAS system?

danaskazlauskas — Fri, 18 Feb 2011 12:48:53 GMT

OK, but how about the performance impact? Data ONTAP is not an idle OS - it constantly works calculating RAID parities etc., so IMHO one aggregate with Data ONTAP and data could have degraded performance.

BR,

Danas

Re: How to get the most usable space having a few disks in FAS system?

vmsjaak13 — Fri, 18 Feb 2011 12:50:53 GMT

Performance impact is very minimal.

Calculating raid parities is done by the CPU, not by the aggregate.

Niek

Re: How to get the most usable space having a few disks in FAS system?

danaskazlauskas — Fri, 18 Feb 2011 15:16:36 GMT

Thanks, Niek and Eelco.

BR,

Danas