Adding capacity to a RAID array

(I’ve been away from the keyboard for a while, and needed to get the fingers working again, so I’ve stayed away from anything new we are doing so as not to upset the marketing lads any more than usual and have gone for something simple to get the hang of this again )

There are two ways of adding capacity … I call them horizontally and vertically. By horizontally I mean across the array … adding more drives to an array to increase it’s size.

Adding capacity vertically is what I call the ability of a RAID controller to increase the size of an array by using additional space that may exist on the disks already in the array.

Thinking horizontally …

The most common expansion request we get is whether you can just add a drive to an array and increase it’s size. The basic answer (without all the caveats) is yes. Add the drive to the system (hot swap is always good as you don’t have to bring the system down), then go into Adaptec Storage Manager, right-click on the array and “reconfigure the array”. Simple. Choose all the drives, RAID type and set your capacity.

Thinking vertically …

This one is not so obvious. It’s basically the same approach - reconfiguring the array but just choosing a new size. Lots of people just seem to miss the fact that you can use the same disks etc, just increase the size. Of course there needs to be space on the disks, but you might have deleted another array freeing up space, or, heaven forbid, changed the drives over to larger disks by using the dreaded “replace one at a time and let the array rebuild” method. Note that there is also another way that we don’t advertise to migrate an array from one set of drives to another set, but I’ll put that one in a separate blog.

Either way, if there is space available on the disks you can grow the array without any great hassle.

Note that you can do this live without shutting down the system (read the caveat about hot swap drives). The RAID card will just chug away in the background expanding the array while you are still using the system. Will there be performance degradation? Yes. Will it kill your system? No. Do it over the weekend.

Now the caveats …

HostRAID cards don’t go past 2TB. If you want >2TB from Adaptec look at our 2, 3 and 5 series Unified Serial cards.

There are a couple of major issues here which revolve around the OS, not the RAID array. XP 32 does not support greater than 2TB - end of story. Other, newer Windows OS do support greater than 2TB (check the limits with the vendor), but not for the boot volume. There is nothing you can do about these limitations, and for that matter there is nothing we can do about it either.

2TB? Sounds big, but today it’s an absolute no-brainer to break this limit so check out your OS as well as your RAID card before going big.

There, 10 minutes of typing and I feel all warm and bloggered again - that’s better.

Ciao
Neil