Best practice order of operations for multiple disk replacement

[josh1014]

Hi, I am about to make some changes to my array and was wondering if someone could confirm best practice.  I currently have a 4TB parity disk, four 2TB data disks and one 4TB data disk.  All disks are healthy and parity is valid.  I have three new 10TB drives.  I am planning to add dual 10TB parity disks, convert the current 4TB parity disk into a data disk, and remove a full 2TB data disk and rebuild its data onto a new 10TB data disk.  

 

I was planning on pre-clearing each of the three new 10TB disks before making any changes to the array.  Could someone please tell me the best practice order of operations to follow after I am done pre-clearing all the new disks?  Thanks!

[JonathanM]

Is all your data backed up to other media?

 

Do you want fastest or safest or something in between?

[josh1014]

No data is backed up outside of the array.  I suppose I would like safest.  

[John_M]

I think I would do this:

• Add the second parity disk (10 TB) and wait for parity to build
• Replace the first parity disk (4 TB -> 10 TB)
• Replace the data disk (2 TB -> 10 TB)

It would not be a fast method but it's safe because the array would be protected by at least one parity disk at all times. The task of upgrading involves writing 3 x 10 TB of data and my choice needs the three writes to be done one at a time. There are faster methods that write two disks in parallel but leave the array unprotected.

[John_M]

And I'd use the removed 2 TB disk to begin a backup of as much of my data as I consider to be irreplaceable.

[josh1014]

If you follow those instructions and add the second parity disk, wont it only use 4TB of the 10TB when creating parity, and then when you replace the primary parity disk, will it again match the 4TB and therefore not expand the max disk size of the array up to 10TB?

[BRiT]

No. Parity is always the full drive size.

 

[trurl]

1 hour ago, BRiT said:

No. Parity is always the full drive size.

To elaborate, the portion of parity that is larger than any of your data disks is filled with zeros, which is the correct value for parity for those portions.

 

Or to put it in a more general way, any disk that is smaller than parity has the value zero for the parity calculation for those parts that are beyond the size of the disk.