1- Pool A can be expand by add one or more disk groups?
- Think of the building blocks like this VDISK->POOL->VOLUME
- The volume can never consume any more space than the pool has in it
- The pool is made up of space from one, or more, disk groups
- A disk group is any set of physical disks
- For best performance and availability, you *should* add new disk groups in the same manner that you started with
Since your (standard tier) disk group is currently made up of 10 x 600GB SAS disks, you (don't have to but) *should* create a new disk group of 10 x 600GB SAS disks. If you buy (and create a disk group of say) 4 x 600GB disks this time, and 6 x 600GB disks next time, and so on then you can get your self into trouble in terms of meeting your availability and performance objectives.
2- The volume which is mapped to host can be expand when adding one or more disk groups to Pool A?
- The "volume" is a decoupled virtual aspect of the storage system. Because the pool is virtual, the volume size isn't directly related to the space availble in the pool. You can make a 10TB virtual volume on a 500GB pool or a 500GB virtual volume on a 10TB pool. This freedom allows you to add space as needed. For example, I can create a 10TB volume, present it to windows, and then grow the back end storage as needed to support it. However, you run the risk of running out of physical space if you don't stay ahead of it. To be careful, it's good to not provision any more size in volumes then you physically have available of usable space.
- So, the answer to your question is that you can technically expand the volume whether or not you add more disk groups but you'll run out of physical space and be in a world of hurt. So, yes, in your case, buy some disks, create a disk group, add the disk group to the pool, and expand your volume. This is safest.
The MSA P2040 currently has 2 free disk slot, if i plug 2 spare disks in to the MSA P2040, Can i add 2 spare disk to current disk group ? or i have to create an new disk group in Pool A in order to expand the volume which is mapped to host ?
- So, you must have a large form factor base shelf then if you only have 12 slots. In a perfect world you would purchase a new (empty) shelf and install 10 x 600GB SAS drives in it, bind those up in a disk group, and present the group Pool A.
- The new shelf can be small or large form factor but you *should* use the same capacity (and speed) of drives.
- I would order at least one extra drive and mark it as a spare drive. You are taking some chances by having 10 drives in a RAID5 without a spare and you are increasing your odds of failure by going to 20 drives so it would be wise to add a "spare" so that the drive can take over immediately upon failure of one of the other drives. This gives you more time to get the failed drive replaced (which you would then mark as a spare since your previous spare would be used).
I hope this is helpful. I'm trying to lay out best practices to save you some grief but there is nothing technically stopping you from doing anything different. You could create a RAID1 disk group of 2 x 1.8TB drives and add them to the pool, you could add a RAID6 group of 300GB drives, you can do virtually anything you want but best practices dictate that you keep it consistent with what you have already.
