I have four 1.5TB drives in my array, and one has just thrown a bunch of I/O errors and gone DSBL.  I'm going to shut it down and check the physical connections, etc, but assuming it's dead, can I replace it with a 2TB drive, i.e. larger than the current parity drive?  I want to restore redundancy ASAP, and I can't find any 1.5's available locally.

You need to do what's called a "swap-disable", whereby you replace your parity disk with the new, larger disk, and use your existing parity drive to replace the failed disk.

 

Read the details in the Wiki here:  http://lime-technology.com/wiki/index.php?title=UnRAID_Manual#Replace_a_failed_disk

 

With one drive failed, the parity drive is the only thing providing the data that used to be on that drive.  How can I replace the parity drive without losing data?

OK, never mind, I read the link you cited.  Thanks, I'll give it a try tomorrow.  Fingers crossed.

UnRAID is designed to do exactly that -- just follow the procedure outlined in the Wiki.

 

It will copy the old parity drive to the new drive;  THEN do a rebuild of the failed disk onto the old parity drive.    As I noted, the procedure is outlined in detail in the Wiki reference I gave you.

 

For convenience, here's the text from the Wiki:

 

-----------------------------------------------------------------------------------------------------------------

 

You must replace a failed disk with a disk which is as big or bigger than the original and not bigger than the parity disk. If the replacement disk is larger than your parity disk, then the system permits a special configuration change called swap-disable.

 

For swap-disable, you use your existing parity disk to replace the failed disk, and you install your new big disk as the parity disk:

 

Stop the array.

Power down the unit.

Replace the parity hard disk with a new bigger one.

Replace the failed hard disk with you old parity disk.

Power up the unit.

Start the array.

When you start the array, the system will first copy the parity information to the new parity disk, and then reconstruct the contents of the failed disk.

 

 

Well, I did as instructed, but after powering back up, I see

 Disk status
  	Model / Serial No. 	Temperature 	Size 	Free 	Reads 	Writes 	Errors
parity 	Missing 		- 		- 	- 	- 	- 	-
ST31500341AS_9VS32171		1,465,138,552
disk1 	ST31500341AS_9VS32171 	38°C 	1,465,138,552 	- 	- 	- 	-
disk2 	ST31500541AS_6XW01X0V 	33°C 	1,465,138,552 	- 	- 	- 	-
disk3 	ST31500541AS_9XW0DVCD 	35°C 	1,465,138,552 	- 	- 	- 	-
cache 	ST3160827AS_4LJ1JF63 	34°C 	156,290,872 	- 	- 	- 	-

Command area
Stopped. Invalid configuration. 		Too many wrong and/or missing disks!

 

The Parity drive has a red dot, Disk 1 has a blue dot, and the Start button is grayed out.  If I go to the Devices screen, I see it has detected the new 3TB WD drive and has it selected as the parity drive, so it seems that it kinda knows what I want to do but hasn't automatically implemented the reconstruction process described in the manual.

 

I'm open to suggestions where to go from here.  I guess I need to somehow commit the new configuration?

 

It looks like you're running v4.7 ==> that does NOT support drives > 2TB.

 

You'll need to use a 2TB drive for the replacement.

 

It MAY be possible to upgrade to v5 at the same time as you're doing all this, but I wouldn't take that risk if you need the data on the failed drive.  Pick up a 2TB drive and then follow the swap-disable process.

 

 

Once you've got everything back in good condition, you can then upgrade to v5;  replace the parity drive with the 3TB drive you have;  and then either keep the 2TB drive as a spare; add it to the array; or replace one of the 1.5TB drives with it.

 

Well, I discovered I had a spare identical 1.5TB Seagate drive, so I swapped it in for the dead drive but unRAID refused to use it because it was reporting a smaller capacity than the rest of them.  A little digging found the forum article about HPA, and by using the referenced hdparm -N method, I was able to reset it to full capacity.

 

The array is now rebuilding, and I'll look at migrating to unRAID v5 another day.  Thanks again for your help.

Once the rebuild is completed, I'd do the following ...

 

(a)  Run a parity check to confirm all is well;

(b)  Upgrade to v5RC16c

©  Replace the parity drive with your new 3TB drive

 

... then you'll be able to use 3TB drives for any future rebuilds and/or add up to 3TB drives as additional drives as your space requirements grow