I currently have an array of 4 TB drives with 2 parity drives. I'm upgrading one of my parity drives to begin the process of moving to larger than 4 TB drives.

 

Can I add it as an unassigned drive and pre-clear it before doing the parity swap or will it be ignored/error because it is larger than the 4TB parity drives? If so, what is the process?

To preclear a new larger drive using the dd command, the process is straightforward, but note that using the Preclear plugin or the Unraid GUI tools is usually safer and more efficient for this purpose. If you still prefer using dd, here's how:

Preclear a Drive with dd

Identify the Drive:

Use the command lsblk or fdisk -l to identify the drive you want to preclear (e.g., /dev/sdX).

Double-check to ensure you're targeting the correct drive, as dd will overwrite all data.

Run the dd Command:

To write zeroes across the entire drive:

dd if=/dev/zero of=/dev/sdX bs=1M status=progress

Replace /dev/sdX with the correct drive identifier.

 

Verify the Drive is Cleared:

Once the process completes, you can check the drive with

hexdump -C /dev/sdX | head

This should show zeroes if the drive was cleared.

 

Notes About Preclearing

Why Preclear?:

Preclearing ensures the drive has no issues (bad sectors) before adding it to the array.

It avoids downtime by preparing the drive before it is added to the array.

Parity Swap Process:

Unraid will allow larger drives as parity drives. The preclear step is separate and doesn't depend on the current array size.

You can preclear the drive while it's unassigned, and once completed, perform the parity swap.

Use Preclear Plugin:

The Preclear plugin automates this process and logs detailed results, making it a safer option.

 

https://docs.unraid.net/unraid-os/manual/storage-management/

 

 

4 hours ago, bmartino1 said:

To preclear a new larger drive using the dd command

Just to be clear, dd won't preclear a drive, since it requires a specific signature to be written after zeroing it, in the OP case the disk doesn't need to be cleared, but if you want to test it, a preclear cycle is better than using dd, since it also reads the disk, an extended SMART test is also a good option, write only is not much of a test, since disks tend to fail more during reads, not writes.

 

 

11 hours ago, JorgeB said:

Just to be clear, dd won't preclear a drive, since it requires a specific signature to be written after zeroing...

 

 

Didn't know that. That explains a few things.