I found this old topic, but comments there indicate it doesn't work for recent 5.0 RCs. Conceptually it would seem to work regardless of the unraid version, but the specifics of adjusting and trusting the array to remove the drive may have changed.

 

I've got an old 500GB drive that appears to be failing. I'll be replacing it with a 1TB drive, so my plan is to:

1. Parity check existing array

2. Preclear the 1TB drive.

3. Add the 1TB drive

4. Copy contents of failing 500GB drive to 1TB drive

5. Zero the failing drive

6. Remove the failing drive

 

Of course the specifics of step 6 are the key to maintaining parity. I've currently shut down my server entirely until the replacement drive arrives, so I don't have the webui up to examine what buttons are available there. Seems like there was a"trust array" option that could be used, followed by a parity *check*.

 

Suggestions?

It should work if you zero the /dev/md device and then check "parity is correct" after running "New Config". Worst case is the parity won't be correct and you rebuild...

Suggestions?

Yeah, don't. Just pull the 500GB and replace it, boot up and let unraid do its thing and upgrade onto the new 1TB drive. Backing up your flash drive, a parity check and smart reports on all the drives before you start would be good too, and if the 1TB is untested, a preclear cycle wouldn't hurt.

 

Otherwise, you are going through unnecessary steps and accomplishing the same thing, only you are erasing the 500GB in the process instead of keeping it intact in case something goes wrong with the rebuild.

 

My suggestion.

1. preclear 1TB

2. back up flash (especially super.dat)

3. parity check

4. smart reports

5. swap 500GB for 1TB

6. let unraid rebuild drive

7. parity check

As jonathanm noted, your steps are NOT what you want to do.    There's no built-in way to remove a drive from an array while maintaining parity [completely zeroing it and then just doing a New Config and clicking the "Trust Parity" box will work; but simply rebuilding the drive is a better and quicker approach].

 

Pre-clearing the 1TB drive does not save any time; but if you haven't already thoroughly tested the drive through some other mechanism (vendor's utilities, etc.), then it's a good test of the integrity of the drive. 

 

After you've tested the 1TB to your satisfaction, just follow the process jonathan outlined => do a parity check to confirm all's well; shut down; replace the 500GB drive with the 1TB drive;  then boot the system and start the array ... it will then rebuild your drive and you're done.    A confirming parity check after it finishes is a good idea.

 

Thanks for the quick responses.

 

The new drive is an advanced format drive, while the failing one is not and is not 4K aligned. That was one reason I was considering the roundabout route. Suggestions for a good way to correct this after the rebuild? I'm familiar with moving partitions around with gparted, but never in this environment.

Thanks for the quick responses.

 

The new drive is an advanced format drive, while the failing one is not and is not 4K aligned. That was one reason I was considering the roundabout route. Suggestions for a good way to correct this after the rebuild? I'm familiar with moving partitions around with gparted, but never in this environment.

Simply pre-clear the drive with the "-A" option.  That will set the partition to begin on a 4k boundary.

Then just use it to replace the existing smaller drive.

 

unRAId will use the partition you created in the preclear operation.  You do not need to do anything more.  You do not need to "move" the partition yourself.

 

Joe L.

I guess I don't understand - the responses above suggested I rebuild from parity to replace the drive, rather than take my roundabout route. Won't that overwrite the partition table on the new drive, no matter what I do with pre-clear?

I guess I don't understand - the responses above suggested I rebuild from parity to replace the drive, rather than take my roundabout route. Won't that overwrite the partition table on the new drive, no matter what I do with pre-clear?

no, unRAID should (from my understanding) use the partition as already defined.

To clairify, the "partition" is part of the RAID array, not the MBR area preceding the partition.  That initial MBR/GPT area is always set up by unRAID.  Since it is always set by unRAID, it is not protected by RAID calculations. (and there is no need for it to be.)

 

If there is no existing partition defined in the MBR/GPT area that is unRAID compatible, it will create the partitioning based on the "default" alignment as specified in the unRAID settings.

 

If there is an existing unRAID partition (or preclear signature) it will (should) use that existing partitioning.

 

So yes, preclear with "-A", set your default partition format to MBR-4k-aligned, and just install the replacement drive and let unRAID re-construct onto the new disk's partition.

 

Joe L.

Ah... that makes sense then. I thought it was bit-for-bit parity at the device level, but it's actually at partition level. Thanks for the info!

Ah... that makes sense then. I thought it was bit-for-bit parity at the device level, but it's actually at partition level. Thanks for the info!

Exactly.  It then lets the partitions start at various (but known) locations.  First bit on each partition results in parity bit stored on the parity disk (interestingly, on its own "partition".  Yes, parity disk is partitioned, but its partition contains parity calcs instead of file-system.)

 

Joe L.