Data ONTAP Discussions

[help] Adding disk to an Aggregate

Good Day.

I am about to expand the capacity of one of our aggregate. Is this command is safe to execute or do i have to set some parameter before executing this command.

aggr add aggr_name  3

I hope somebody could confirm it.


Re: [help] Adding disk to an Aggregate


Yes it is safe to execute. You can add disks to a raidgroup in an aggregate while the system is up and running. If you execute this command without specifying a size in GB the smallest spare disk in the pool wil join the aggregate first. If you do not specify the -g option the disks will be added to the last raid group you created until the maximum raid group size has been reached. e.g if  your raidsize is 16 and your last raid group currently contains 14 disks. if you add 6 disks.2 disks will be add to the existing raid group. 4 will be added to a new raid group.



Re: [help] Adding disk to an Aggregate

Hi, welcome to the community

You have not said how many disks you are adding but if you have run out of space and you are adding a single disk, it can reduce performance.  This is because the all the write operation go to the single empty disk until it is filled to the same level of the other disks in the aggregate.  Also all the reads will be from just one disk, if that is where the data was written so the data can take a long time to balence.

We have hot added disks to aggregates many times and it is safe.

  1. Hot connect disk shelf
  2. assign software ownership - filer cluster pair
  3. add disks to aggregate - Best option is full raid group of new disks
  4. OPTIONAL - reallocate aggregate if support on your system or reallocate each volume in aggregate - see link below

Hope it helps


Re: [help] Adding disk to an Aggregate

Thank you for the reply.

You have mentioned that the command will assign the smallest spare disk in the pool.

So i think its better if I  pick the disk to be added. Our  spare pool consist of 147 and 300 Gb spares

and the target aggregate is consist of 300 G disks.

how about executing aggr add aggr300 -d disk1 disk2 disk3 instead of aggr add aggr300 3. Is it same.

Thank you again.

Adding disk to an Aggregate


the command

aggr add aggr300 3

will add the smallest disk in the pool to an existing raid group,but it will not add smaller disks than the ones that are already part of an existing raid group.

This command

aggr add aggr300 -d disk1 disk2 disk3

may take a bit longer to type than this

aggr add aggr300 3

command, but you can control which disks are added to the aggregate.