Another Pool or Disk Group

Hi

With MSA2060 SAS.

We currently have a disk group with 9 disks (SSD RAID5) in Pool A. 

Now we want to expand the storage with another disk group (9 disks again SSD RAID5).

What is the recommended configuration?
Additional disk group in pool A?
New disk group in pool B?

The spare disk can be used in both variants in any case, right?

Thanks.