Need to add disks in the newly installed disk shelf to the existing aggregate.

[Naveenpusuluru]

Hi Techies,

We have a cluster with 2 nodes and running on data ontap version 8.3.1 c-mode.

We have two SAS aggregates hosting on each node and raid group size is 17.

We have installed new disk shelf with 24 drives. I want to add the new disks to the exising aggregate. But with the current raid group settings i can able to add only 17 disks to the existing aggregate. Remaining 7 drives will be not used.

I don't want to waste those disks as spares, what i am planning is i want to change the aggregate raid group size to 20 and add the 3 disks to the existing raid group and create a new raid group with 20 disks.

Please suggest me how to proceed with this.

[JGPSHNTAP]

Go into advanced or diag mode

run this

storage aggregate show -fields maxraidsize

that will show you the size

storage aggregate modify ?  

Follow the settings.  

[Naveenpusuluru]

Hi @JGPSHNTAP

Thabks for the commands, I know all the commands. I am looking for best practices not commands.

[JGPSHNTAP]

This statement "Please suggest me how to proceed with this"

Let me to post the above.

[JGPSHNTAP]

The first thing you do is modify the raid group size and then add the drives.  

and you cannot undo so make sure you do it right the first time

[Naveenpusuluru]

Hi @JGPSHNTAP

Sir, i have already mentioned the raid group size also in the post. Anyway thanks for your reply ... 🙂

I will take care of it.

[Naveenpusuluru]

Hi @JGPSHNTAP

I know the process and commands. I am looking for best practice. thank you ... 🙂

[JGPSHNTAP]

Not once in your post did you ask for best practice to add drives.

If you are looking for SAS, 24 is a good number.  

[Naveenpusuluru]

Hi @JGPSHNTAP

Sir,

I have not asked for commands. Please go through my post, i have explained my plan also.

Thanks ... 🙂

[paulstringfellow · Accepted solution]

RAID group sizing is always a littel awkward, but you are basically looking for good logical splits.

as one of the responses mentioedn 24 for SAS is not a bad idea, but as you've said it's really about logical bounderies.

nothing wrong with your original idea, make it 20.. add three drives and then a new RG of 20 and add them to aggregate is all fine.

personally i try to keep my boundaries to shelves.. hence 24 a good number, so if i add a full shelf, i'm getting the optimum capacity without drives getting left over.

there are some suggestions around whether you want capacity or resillience, so smaller RG's provide less performance, but in the event of failures have quicker rebuild times etc... but often these aren't huge considerations.

one thing you didn't say was you current setup.. so two 17 drive aggregates, so what is that 36 disks, with 17 in RG's and a couple of spares?

not sure if this all helps.. but your original plan is solid enough, just think of next time you add a shelf.. you'll end up with a similar problem.

[Naveenpusuluru]

Hi @paulstringfellow

Sorry. Both aggregates contains 2 raid groups of 17 drives.