RAID questions/server research

***Keep in mind I am going with a custom built server and NOT looking for some proprietary DROBO type crap***

So I'm researching/planning out a massive (for me) file/media server and coming up with more and more questions. Especially regarding RAID. Now up until a couple of days ago, I was still in the ancient thinking that once you created an array that was your array. Want to keep your data and expand? Too bad! However, in my research I kept seeing people mentioning what sounded as if they were expanding their arrays over time with additional drives. I looked into it more and what do you know, the card I just got (Areca ARC-1260) for my future beast supports "online expansion." That's great. Now I can build this thing 2TB at a time.

But now I have more questions. To start the thread off, what about upgrading drive sizes? Now my impression is that the array has to use the same size drives. i.e all 1TB drives or if you throw a 2TB in with them it will only use 1TB of it. Or has this changed like the expansion capabilities? So the issue: what happens when I fill all 20 bays with 2TB drives in RAID 6 (hardware) and get to the point where nearly all that space is filled? Now I want to start gradually replacing those 2TB drives with 4TB drives without losing my data. How would one go about upgrading that as I obviously don't have a 20TB external drive to pull out? Anyone else run into similar issues or have any thoughts/ideas on that?

For those that are interested, the current planned specs (will be updated as changes are made):

Case: Norco RPC-4020 4U 20bay Hot Swap Case
Mobo: Gigabyte something or other, I can't remember the exact model now
CPU: AMD X2 Dual Core 2.6Ghz
RAM: 4GB PC2-1066
RAID: Areca ARC-1260 16 port PCIe 8x (does RAID 5 and 6!)
HDD: WD 2TB Drives

You have no option you will HAVE to offload the data to upgrade.

What about replacing the drives 2 at a time (raid 6 handle 2 drive failures) with larger drives, will it then just use the same amount of the larger drive (i.e. still only 2TB of the new 4TB drive)? And then once all of them are replaced, expand the array and volume?

You could only replace 2 drives..

You cant expand a Raid 0 or 1 to 5 or 6

RAID 6 will sustain 2 drive failures at a time. So replace them in 2's until it is all replaced. Nothing says that you can only replace 2 and then you're done.

I wasn't talking about migrating from one raid level to another and only RAID 6 (and very little raid 5) will be considered in this build. You CAN expand the raid 6 array from say 5 drives to 6, 7, 8 and so on along with the volume size as well to utilize that extra space.

satan..
two drives out of a raid 6 array are the two drives that can fail.

you cant magically make another 2 reappear.

Adragontattoo said:

satan..
two drives out of a raid 6 array are the two drives that can fail.

you cant magically make another 2 reappear.

Click to expand...

I think he's suggesting to fail two drives that you want to replace with larger drives, replace with said larger drives, and rebuild.

I would guess, though, that if you're replacing an array of 1tb drives with a few 2tb drives, they may only see 1tb of the drive. I'd want to doublecheck that first.

I'd hit up the storage section @ 2cpu.com, lots of areca experience there for sure!

Yes cw, that was the point. fail the 2 drives, replace with larger drives, rebuild, rinse and repeat. And yes, it should only see/use the same amount of the new drives as were already in there (i.e. replacing a 1TB with a 2TB would still only see 1TB), but once all of the drives have been replaced with the larger ones you could then expand the array and volume. Right? Or can you only expand to add an additional drive, but not expand to use more space on an existing drive?

THanks for the heads up about 2cpu, i will definitely check it out.

Yes cw, that was the point. fail the 2 drives, replace with larger drives, rebuild, rinse and repeat. And yes, it should only see/use the same amount of the new drives as were already in there (i.e. replacing a 1TB with a 2TB would still only see 1TB), but once all of the drives have been replaced with the larger ones you could then expand the array and volume. Right? Or can you only expand to add an additional drive, but not expand to use more space on an existing drive?

THanks for the heads up about 2cpu, i will definitely check it out.

Taking cw's advice, I found a similar topic on the 2cpu boards and was able to reask my original question on it. I did get a confirmation on that idea (at least with the Areca 1260 card). So, if you have 1TB drives in your array and swap them out with 2TB drives and rebuild, the array will only address the original 1TB. Once you have replaced ALL of the drives with the new 2TB drives, you can then expand the _volume_ (not the array) to the new extra space. Anyone interested can find the original thread on the 2cpu boards here: http://forums.2cpu.com/showthread.php?t=94532&highlight=areca+1260

SatanSkin said:

Taking cw's advice, I found a similar topic on the 2cpu boards and was able to reask my original question on it. I did get a confirmation on that idea (at least with the Areca 1260 card). So, if you have 1TB drives in your array and swap them out with 2TB drives and rebuild, the array will only address the original 1TB. Once you have replaced ALL of the drives with the new 2TB drives, you can then expand the _volume_ (not the array) to the new extra space. Anyone interested can find the original thread on the 2cpu boards here: http://forums.2cpu.com/showthread.php?t=94532&highlight=areca+1260

Click to expand...

Glad you got your answer. I lurk over there to sell stuff and to get storage questions answered, for the most part.