Hi All

 

I needed to pre-clear a disk for a mate over the weekend, so I removed a data disk from my production server in order to free up a slot for the disk to be wiped. The system warned me that it was running with no protection, which was fine, and I started the pre-clear.

 

However this morning I just realised that there were some changes to data over the weekend as there is a live SQL/Webserver VM hosted on this box!!

 

So my question is - when I replace the original data disk it may have data from Friday on it rather than updated data... will UnRAID give me the option to update the data disk with whats on the parity drive, rather than updating the parity disk with whats on the data disk?

 

In hindsight I should have pulled the parity drive and used this slot for preclearing the disk... but unfortunately I didnt think about it!

 

Of course, it might be that the changed data is on another disk - but I just thought I would get some advice before replacing the data disk later on!!

 

Thanks

 

SM

Sorry... forgot to say - I have v6.3.5

 

50 minutes ago, SliMat said:

So my question is - when I replace the original data disk it may have data from Friday on it rather than updated data... will UnRAID give me the option to update the data disk with whats on the parity drive, rather than updating the parity disk with whats on the data disk?

This is an incorrect description of how things work so you are not offered either option in the way you describe it..    You have to either rebuild parity from the disks (thus losing any changes over the weekend) or rebuild the data disk (which keeps the changes).

 

unRAID will have been emulating the missing disk, so any updates over the weekend will have been applied to the emulated drive which includes updating parity.    When you re-insert the disk then unRAID will give you the option of rebuilding it to match the 'emulated' drive.   Note that the rebuild is not purely from parity - it uses the combination of all the other data drives plus the parity drive to handle the emulation so it is important that the other disks are good for the rebuild to be completely successful.

 

Note that to force the rebuild onto the same drive as was there previously you need to have started the array with the old disk missing to get unRAID to forget its serial number.  Not sure if you have already done this from your description.   When you put the old disk back you then need to stop the array and re-assign it to get unRAID to rebuild it including the data updated over the weekend

Hi itimpi

 

Thanks - yes, I started the array with the disk missing in order to keep the server online...

 

So what I need to do is rebuild the data disk in order to keep the changes.

 

My concern is that, rightly, by default UnRAID will write corrections to the parity drive and what I want to make sure is that when I reinsert the data disk it can be forced to assume that the parity disk is right and so will 'correct' the data disk with the emulated disk data - so keeping nay changes.

 

I assume that I can uncheck the "write corrections to parity" box in order to ensure that it doesnt 'correct' the parity disk.

 

Thanks

 

 

18 minutes ago, SliMat said:

My concern is that, rightly, by default UnRAID will write corrections to the parity drive and what I want to make sure is that when I reinsert the data disk it can be forced to assume that the parity disk is right and so will 'correct' the data disk with the emulated disk data - so keeping nay changes.

 

I assume that I can uncheck the "write corrections to parity" box in order to ensure that it doesnt 'correct' the parity disk.

 

You'll be rebuilding a disk, not running a parity check, there will be no option for correcting parity.

7 minutes ago, johnnie.black said:

 

You'll be rebuilding a disk, not running a parity check, there will be no option for correcting parity.

 

Thanks Johnnie - that makes a bit more sense... I was thinking that it would be re-including the data disk in the array and then using the existing parity data to update the incorrect bits on the data disk.

 

Thanks

I was thinking that it would be re-including the data disk in the array and then using the existing parity data to update the incorrect bits on the data disk.

 

That's what you'll be doing, data will be rebuilt from current parity plus all other data disks, exactly the same data you see on the emulated disk now.

 

 

Thanks - that'll teach me to use my live system to do a favour! Wish I'd found an old carcus and created a new UnRAID system to preclear this disk!