Another RAID Question

[cDuck28Z]

I just finished building a pretty powerful machine, but I haven't bought any HDD's yet. I want to make sure that I can expand my storage in the future, and would like to run a RAID setup. Would it be possible to take 2 2TB drives and set them up in a RAID 0, and use a 4TB drive to run a RAID 1??

I only ask because I only need 2TB of storage right now, but in the near future, I may be expanding to 4TB and would like to keep at least a RAID 1 on all my information.

 

[Alexffiala]

Should work, no problems I can think of.

 

[PP Mguire]

So you want to RAID 0 2 2TB, and have that RAID 1 with a 4TB for the mirror? I don't think you'll be able to RAID a RAID. If you plan to buy the extra drives later you would have to reconfigure to probably RAID5.

 

[Alexffiala]

I think he meant he wanted to increase his storage capacity to 4TB but maintain raid 1.

So couldn't he just get another 2TB for a total of 4TB and get another 4TB drive as the mirror?

 

[PP Mguire]

I think he meant he wanted to increase his storage capacity to 4TB but maintain raid 1.

So couldn't he just get another 2TB for a total of 4TB and get another 4TB drive as the mirror?

Exactly what I said. He would need to RAID 0 the 2x2TB setup, then try to RAID 1 the RAID 0. See what I'm saying? Don't think it'll work that way. A better choice would be RAID 5 all 3 drives because IF he was able to RAID 1 off the 0 it would slow it down to the single drive speed. (Copying over to the 1 as opposed to the speed of the striped 0)

 

[cDuck28Z]

Wouldn't setting up a RAID5 with a mix of 2TB and 4TB drives revert all of the drives down to a maximum of 2TB? Seems wasteful to even buy a 4TB at that point?

 

[PP Mguire]

No it should only combine all the drives into a single partition while losing some space for parity. Even still, you're getting the speed of RAID, and the parity of 5 rather than wasting a whole 4TB of space for RAID 1.

 

[Yevrag35]

What about doing a RAID 10 instead of 5?
Take your two 2TB drives and instead of buying one 4TB drive, buy two more 2TB drives.
This would allow, essentially, two striping drives and two more drives mirroring those drives. Your total usable space would still be 4TB, but this way you don't get the performance loss that RAID 5 gives.

 

[PP Mguire]

5 is a stripe with parity, I fail to see how that's performance loss. My friends 16TB RAID 5 array sustains over 200MB/s either way.

 

[Yevrag35]

5 is a stripe with parity, I fail to see how that's performance loss. My friends 16TB RAID 5 array sustains over 200MB/s either way.

Raid 5 and 10 should read at the same speed, but 10 generally trumps 5 at writing because it doesn't need to manage parity. Hence, that's why a lot of databases are in raid 10 configurations.
Now, on the other hand, if it's cheaper to do raid 5, then I wouldn't bother.