NetApp 2020 with two controllers

I am configuring NetApp 2020 which have two controllers. The storage has 12 disks with 1TB capacity each. I want to remove one controller and use the diskes which are owned by this controller. Should i remove Aggr0 from the controller i am going to remove.

NetApp 2020 with two controllers

I do not dive into the process of making a HA system non-HA...

You'll have it easier when you remove the aggr0 first, then the disks are "Spare" Disks and can easily reassigned to the other controller.

All this can be done in the Special Boot Menu (option 5, Maintenenace Mode).


NetApp 2020 with two controllers

Thanks for your prompt reply. Actually we have no intention of removing one controller, but with the existing scenario with 2 controllers in place, each controller will take 4 disks (1 data, 2 parity and 1 spare), and there will be very little disk space that will be alloted for the data. The client in the future, plans to add more disks, but currently the data requirement is of prime importance.

If possible, please can you specify what needs to be done under the Special Boot Menu - option 5: Maintenance Mode trhat you had mentioned. Since it is my first time to configure the filer, I will be thankful if you could provide me the necssary steps.

Re: NetApp 2020 with two controllers

No problem... Lets say filer1 stays and filer2 will be the backup node...

reboot filer2

when it prompts for pressing "CTRL-C for Special Boot Menu"... press CTRL-C (see further below)

then you get the Special Boot Menu:

(1)  Normal boot.

(2)  Boot without /etc/rc.

(3)  Change password.

(4)  Assign ownership and initialize disks for root volume.

(4a) Same as option 4, but create a flexible root volume.

(5)  Maintenance mode boot.

then select (5) and after the messages on the prompt

*> disk remove_ownership

this will ask you if you want to remove the ownership from the disks owned by this controller, answer yes.

THEN reboot filer1 (maybe not really necessary)

when finished and logged in (no need for Special Boot Menu)

filer1> disk show -n

this should list all the unowned disks, this node sees


filer1> disk assign all

then you should have a few more spare disks and you can create a new aggr or for maximizing the available space in the aggr, you can add them to aggr0.

Good luck!




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Re: NetApp 2020 with two controllers


you can build one controller with a traditionel volumen/aggregat. then you only need 1 x paraty, 1 x data and 1 x spare disk.

you can use this as an active / passive setup. where you can use 1 more data disk in your on your primary storage.

and you have still a HA solution.


Re: NetApp 2020 with two controllers

Hi Peter

I too am in a similar position. We have a 2020 witrh two controllers and 12 disks. We want to maximise available space so were thinking of going the route you mentioned. Does your suggestion still allow the second controller to take over in event that the first controller fails or does each controller have to have an aggregate. Presumably this needs minimum 3 disks as Jakob mentions.

Are there any downsides in having all aggregates as RAID-4?

We will be using the system for file storage and backup virtual machine storage but our live systems run on our new EqualLogic arrays.



NetApp 2020 with two controllers

Jakobs solution is correct to use the least number of disks but still have HA.

Hi Barry,

my suggestion is one with the absolut maximum if sikspace availabl t one controller only, where the second controller is rendered useless... I personaly do not prefer this configuration, because the system has been bought with the HA capability and also should be used this way (licenses are 1.8x more expensive for a HA solution then on a single controller)...

Back to the preferrred solution:

filer1 with 9 disks and RAID-DP

filer2 with 3 disks and RAID-4

this way you keep the HA functionality and mximize the capacity.

I would not use RAID-4 for any productive data and stick with RAID-DP (assuming it is OK to invest one more disk for data availability). Especially since we have these huge disks these days (1TB and bigger) which take hours to rebuild!



Re: NetApp 2020 with two controllers

Thanks Peter. I’ll try the preferred solution.



Re: NetApp 2020 with two controllers

Thanks Peter for your prompt response and the solution.

My another question is that in the future if the client requests for additional disks then I will use the 2nd controller and configure it in the Active-Active mode. During that time, if I have to boot from the 2nd controller, what is the procedure I need to follow so that it can boot properly from the newly installed disks?

Best Regards


Re: NetApp 2020 with two controllers

When you get more disks, they come without any ownership information on them.

This is not an easy one, because then you have to create the root aggr and root vol0 and extract ontap and download and so forth...

You can send me an airline ticket and I'll come and do this for you