How do you save old parity info? AND Unassigning the parity drive.

I've been trying to find definitive info on a couple of things regarding a parity drive upgrade.

 

First, I have found several accounts of how to upgrade the parity disk - none of which are like I've done it in the past.

 

I thought I was done as follows...

 

1 - Parity Check.

2 - Power down server and replace existing parity with new parity HDD.

3 - Power on Server

4 - Array is stopped at start-up recognising old parity is missing (Changed). Assign new drive using the drop-down-box.

5 - Parity Sync.

6 - Parity Check.

 

This is using 5.0.5.

 

Now it would appear the consenus is to unassign the old parity drive first...but this invalidates the parity info on that drive.  So...if a data drives fails during parity sync, how to you use this old parity HDD to rebuild it if the info is invalid?

 

Does the above parity exchange work (1-6), or am I mistaken??

 

 

 

 

Should be no difference. Not sure what you mean by invalid. Is that what the UI says? Old parity isn't changed by unassigning it. Either way will work.

Should be no difference. Not sure what you mean by invalid. Is that what the UI says? Old parity isn't changed by unassigning it. Either way will work.

 

Says in the wiki that the parity is deemed invalid if un-assigned

 

...a user can always deem parity invalid by un-assigning it.

Should be no difference. Not sure what you mean by invalid. Is that what the UI says? Old parity isn't changed by unassigning it. Either way will work.

 

Says in the wiki that the parity is deemed invalid if un-assigned

 

...a user can always deem parity invalid by un-assigning it.

I would interpret that to mean that unRAID would consider it invalid if it is unassigned, and will want to rebuild parity if you reassign it. Don't think it should matter though. I don't think it actually changes any of the parity data when you unassign it, and can't think of any reason why it would.

 

I have done this many times. I just stop the array, shut down, change the disk, start up, assign the new drive, let it rebuild. This applies pretty much whether upgrading parity or a data disk, just some different wording in the UI. In fact I don't think unRAID does any thing differently in either case. Just rebuild from the parity calculation of the remaining disks.

Trurl - good points.

 

My concern is if a data drive dies while the parity sync is in progress. It would mean you don't have valid parity info to rebuild it. Therefore, you would need to put the old one back in. But I don't know the process to make it work.

 

This is especially valid when you look at my parity upgrade thread. I did it the way I always do it. The new drive was faulty, so I just put the old one back in and everything was fine. Then, after reading some stuff here, and the posted replies, I thought I'd done something wrong, so gave it another go. This time when I did it, I un-assigned the parity drive. Unfortunately, the new drive was definitely dead, so I had to put the old drive back in - but this time - I got a massive amount of parity sync issues when carrying out a parity check. Seems un-assigning the drive did make a change.

 

Gives my cause for concern.

If you have not written to the array then you can do a  'New Config'; assign the drives including the old parity disk; and select the Trust Parity option.  It is a good idea to have a screen shot before you do the New Config to make sure you know what the old drive assignment was.

In the special case where you're replacing the parity drive (and not a data drive) "saving the old parity drive" is trivial.

 

Just remove the old parity drive; then replace it with the new one; and let it rebuild.  The simple fact you still have the old parity drive automatically "saves" your parity.

 

Just be CERTAIN that you don't do ANY writes to the array while you're building the new parity info -- if you do, the old drive will no longer have valid parity info.

 

If something should go awry while you're building the new parity drive (i.e. a data disk fails), all you have to do is, as noted above, do a New Config with the "Trust Parity" option [Check the "parity is valid" box] using the old parity drive.

 

 

If something should go awry while you're building the new parity drive (i.e. a data disk fails), all you have to do is, as noted above, do a New Config with the "Trust Parity" option [Check the "parity is valid" box] using the old parity drive.

 

Excellent. I haven't used this part of the software before. Always learning something new. Thank you for all the comments.