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Expand a raid 5 array w/o moving data.

D

drozenski

Limp Gawd
Joined
Mar 9, 2003
Messages
506
Can you expand a raid 5 array in the following way?


Say i had 4 1TB drives that i want to upgrade to 2TB drives.

[1]-[1]-[1]-[1]

Could i add a 2TB drive

[2]-[1]-[1]-[1] ( Rebuild array)

Then continue doing that

[2]-[2]-[1]-[1] ( Rebuild array)

[2]-[2]-[2]-[1] ( Rebuild array)

[2]-[2]-[2]-[2] ( Rebuild array)

Untill all my drives were [2]-[2]-[2]-[2], would the raid auto see the new space and add it to the array? w/o a format?
 
I was just thinking about that scenario the other day... :)
It would be nice if it could be done... but I have a bad feeling it isn't. :(
 
On a decent controller that should indeed work a.f.a.i.k.
If you have a specific controller in mind you might want to test your idea with tech support first though.
 
That would be extremely risky. If a drive fails during that process you lose everything, plus when it's all done you would need to do a further expansion into the full 2tb space of each drive.

What RAID controller do you have?
 
It would be faster and safer to take all the 2TB drives and create a new array and copy the data to the new array.
Take down old array.
 
doable yes but not recommended, better solution to create new array from 2tb drives and move data over.
 
I'm using an onboard intel raid controller.

Building a new array is hard. I would either have to 1. Buy and build a whole nother box. Or 2 buy a raid controller card setup the raid on that.

Either way ends up costing me money

Maybe ill just bring my box to work. We have a 150TB san array. im sure they wont miss a few TB's for a day or two.
 
Do both. Copy your data to the SAN as backup and see if you can do it the way you described in your first post. But I do think you'll need a hardware RAID controller, Intel software RAID I don't think will allow this but it would be nice to try.
 
You'll have to nuke the array and create a new one with the onboard controllers as they don't support capacity expansion, so copying data to your SAN seems like the best method if you're allowed to do so.
 
There was a thread on here not too long ago. Where someone done a similar thing but raid 1, then they had a problem expanding the partitions from the smaller size to new drive's size.

So I would say go with backing up the array first, like others have said.
 
I know you can do this on areca's but I wouldn't do it on raid5. On raid6 I would consider doing it though (one disk at a time). Maybe add a disk go raid 5 -> raid6 and then start replacing them but no way I would do this on raid5.

When I went from 12x1 TB raid5 (yeah I was really greedy) to 20x1TB raid6 I just brought my machine to work and offloaded to two 8x750 GB raid6 2U machines and then whiped the array/fs and copied the data back. I plan on upgrading to two TB drives soon and I already know how I am going to do it:

Take the array offline for a day or two:

Mirror each 1 TB drive to its 2 TB equivelent using a hba/sata controller (non raid) then run the array off 2 TB drives for a while and once I am happy with the array I wil use the 1 TB drives for software raid6 and copy all my data to the software raid and after some stress testing I will finally whipe the 2 TB disk array and create a new array/fs.
 
Well he is using the onboard Intel raid, so what works on Areca doesnt matter, and RAID6 is not an option.

Even if he could do it. Its still a terrible idea and would take forever to complete.
 
fun concept to theorize on but horrible idea that would take weeks of high risk activity that should never be done outside of experimenting on crap data :)

WORST case scenario if you had no access to the SAN, you could get an extra 2TB drive and keep it as a spare for instant replacement of a failed drive and use it to store a compressed, cloned image of the 4X1TB volume which should be like 2.8TB if full uncompressed and fit fine on a 2TB drive (unless it's completely full with already highly compressed HD PRON :). Relatively low cost and very safe because you would maintain both your original RAID copy and your 2TB spare drive image. You could also resell the 2TB right away near cost quite easily if cost is a big issue. This is still tons faster and safer than the original proposed method (it takes 30+ hours to rebuild 3 X 1TB array on 7200 RPM drives, it would take you 3-5 days EACH step with over hundreds of hours of potential data risk).
 
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