VMware Solutions Discussions

Adding a shelf to a FAS2020


Hello to all,

I need to add disk space to my FAS2020. At the moment it only has base shelf with 12x500GB SATA HDDs.
I am using active-active controller and I have two aggregates. I'm thinking of a shelf with 12x1TB SATA HDD. Can I extend my two aggregates of these discs? Or should I choose homogeneous HDDs (so 500 GB HDDs)? In terms of performance, since increasing the mechanics, I should improve, right?

How much space do I get net profit of 12 TB RAW added to this SAN?

Thank you all for your responses, have a nice day.




Well if you are trying to add disks of 500GB aggregate to 1TB aggregate then 1 TB will be downsized to 500GB each. Only then you will be able to add them in 1 TB aggregates on each controller.

However, if space is a concern for you, you need to create a new Aggregate. However since you will only be buying 1 shelf of 12X1TB SATA drives I would recommend to add them to only 1 controller with 1 Aggregate. That will be ideal for performance/space configuration. 

Cheers !


Thank you for your reply!

You have pointed out another interesting aspect, do you think is better to assign all new shelf with one controller? What are the advantages and disadvantages?




do you think is better to assign all new shelf with one controller?

Providing you create new aggregate:

+ you are getting much more usable capacity with one aggregate in this case (single RAID group, so just two drives 'lost' for parity and hot-spares are also per controller, not global)

- one controller will have more work to do - which may, or may not be a concern (depends on its utilisation really)


I take advantage of your willingness, I was told I might have a new FAS2020 with a similar amount of RAW disk space of the shelf at the same price. Do you think it's better to have two rather than only one FAS2020 with the shelf add-on or not? Currently I'm using iSCSI in VMware and in CIFS file sharing. At the moment I do not need to do disaster recovery.

Thank you again,




It's a tough question.

With more filers, you have more things to manage, yet more CPU power & filer memory to play with.

I'd say that if you have more than one discrete workloads, which can be easy separated onto different filers, then why not have two boxes, if that's cheaper than having one, bigger?


Clear and decisive, thanks again!




Hi and welcome to the Community!

Personally I'd opt for 500GB disks - if they are still available. You can then expand each of your existing aggregates, and your performance should improve, as there will be more active spindles (you may consider running reallocate for existing volumes to spread them across all available spindles).

With 1TB disks you should ideally create a new aggregate - if you try to add them to existing ones, each drive will be downsized to 500GB.

BTW - you can connect only DS14 shelves to FAS2020, each holding 14 disks.

You will get around 7TB usable from 12x 1TB aggregate (2 drives left as hot spares).




Thank you for your support!

Now I understand something more about FAS2020


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