The other day, I was pushing at the limits of my existing Infrant ReadyNAS NV
You see, the ReadyNAS uses Infrant's proprietary X-RAID. X-RAID basically RAID 6RAID 5 (see comments, below) with the ability to dynamically increase the total size of the RAID as well.
So, not only will the ReadyNAS run with a single drive faiure (and hot-rebuild the drive), it can dynamically increase the size of the RAID set as well. So, all I had to do was:
Buy four drives of the appropriate size. I went from four 250GB drives with a total size of about 700GB, to four 500GB drives with a total size of about 1.6TB.
The reason you don't get "all" the space on the drives is because redundant information is spread across each drive that allows any drive that goes "down" to be replaced and rebuilt with no data loss.
With the ReadyNAS on, and in use, pull out the first of the four drives.
Yeah. Scary. But that's what to do!
Unscrew the four screws that attach the SATA drive to the tray from and attach it to the new.
Slide the new drive into place.
At this point, the ReadyNAS will automatically rebuild the data that was on the original drive on this new drive. All of this has been done with the unit on and operating.
Wait for the rebuild to complete (it'll send you email when it's done).
Repeat with the next drive.
Yeah. That's it. When you're done, you do need to restart the ReadyNAS to get the volume to expand, but that can be postponed until you're ready to do it... and that's the only time the unit is "down".
Pretty cool, eh?
(Yeah, I know I sound like a pitchman for Infrant, but I'm honestly not affiliated with them in any way at all. I just think it's a great product.)
19 Mar 2007 at 07:01 am | #
Small correction for above - X-raid is basically raid 5 not raid 6 - otherwise it wound N-2 not N-1 as it currently stands, and it could also handle 2 drive failures not one, which it can’t.
That said, the infrant NAS products are pretty incredible, and worth every penny.
19 Mar 2007 at 09:01 am | #
I based the RAID 6 comment on the Wikipedia article referenced above. Specifically, the article indicated that RAID5 will not continue to operate with a failed drive, while RAID6 will, with a single failed drive—that’s what the ReadyNAS does…
But, if RAID5, fair enough!
21 Mar 2007 at 03:06 pm | #
Yeah, the article on wikipedia is actually a little confusing in the way its written, in that it says for RAID-5 “Distributed parity requires all drives to be present to operate” which is misleading - right after that it says “drive failure requires replacement, but the array is not destroyed by a single drive failure.”
I think their definition of operate just means the array is healthy - Raid-5 array’s can continue to operate with a failed drive, its just not advisable for them to, because if a second drive fails you’re toast. That’s the improvement of Raid-6 - your array will not be lost if you loose two disks, but the price paid is that you loose a disk worth of space to parity.
Infrant is definitely based on Raid-5 - otherwise you’d only get 2 disks worth of space out of your 4 disk array.
21 Mar 2007 at 03:29 pm | #
Fair enough, Isaac—I’ve updated the article to reflect this. Thanks!