I've been using unRAID for about a month now and i still don't understand what the "Restore" button does on the main page.  I looked in the manual and i really don't understand what it does. I think i understand after i read it, but then i realize that i don't .  Is this correct: if i move all my data drives into different disk positions and click Restore, will it reset the array and rebuild the parity? So... disk1 becomes disk2 and disk2 becomes disk3 and disk3 becomes disk1 on the Devices page.  Go back to main and click Restore.

 

Thanks.

Restore is in my opinion poorly labeled.  It is a "Reset/Initialise array" button.

 

If you remove a disk from the array you would press "Restore" to reset the array to the set of drives remaining and to build parity on them.

 

If you stop the array and simple re-assign the existing data drives to different positions and re-start it, unRaid will simply record their new positions (as long as they are all there and the parity drive has remained the same)  No need to press the restore button at all in that situation.

 

If you have a drive fail, and parity in combination with the other drives are used to dynamically supply data from the missing/defective drive, then you would NEVER use the "Restore" button. It would erase all traces of the missing/defective drive and re-build parity from the remaining drives. (Some have thought it would restore their data... but instead, because of its poor name, they effectively deleted the failed drive from the array)

 

If you have a drive fail, replace it, then start the array. It will ask you if you want to use it in place of the failed drive. All you need to is Start the array.

 

 

Restore is in my opinion poorly labeled.   It is a "Reset/Initialise array" button.

 

If you remove a disk from the array you would press "Restore" to reset the array to the set of drives remaining and to build parity on them.

 

If you stop the array and simple re-assign the existing data drives to different positions and re-start it, unRaid will simply record their new positions (as long as they are all there and the parity drive has remained the same)  No need to press the restore button at all in that situation.

 

If you have a drive fail, and parity in combination with the other drives are used to dynamically supply data from the missing/defective drive, then you would NEVER use the "Restore" button. It would erase all traces of the missing/defective drive and re-build parity from the remaining drives. (Some have thought it would restore their data... but instead, because of its poor name, they effectively deleted the failed drive from the array)

 

If you have a drive fail, replace it, then start the array. It will ask you if you want to use it in place of the failed drive. All you need to is Start the array.

 

 

 

 

So in another words, the restore button is used when you want to remove an empty drive from the array?  If you don't "restore" it, it will try to generate parity for the missing drive and if you another drive fails, you're SOL.  Or you simply don't want the data on that drive after you've removed it, you just restore, and parity will be generated from the remaining set of drives and hence protected once again.  Am I correct?

so Restore builds/rebuilds the parity drive from the drives that are currently in the array?

Please check out this Best of the Forums link.  A couple of links from the top is a line called "The Evils of the Restore Button".  There are three links that describe what Restore does in some detail.  Normally Restore is not a good button to push, but there are times, like if you ever wanted to remove a drive from the array, that you need to use it.

 

 

so Restore builds/rebuilds the parity drive from the drives that are currently in the array?

It does not "restore" anything. It "Sets a new disk configuration" based on the currently assigned and working drives.  It then immediately invalidates parity and starts the process of calculating parity from the currently assigned and working drives in the array.  You should NEVER use it after replacing a failed drive. Doing so will eliminate any chance of rebuilding the failed drive from parity.

It does not "restore" anything. It "Sets a new disk configuration"

Maybe it should have been Re-Store instead of Restore 

 

It does not "restore" anything. It "Sets a new disk configuration"

Maybe it should have been Re-Store instead of Restore 

 

Still too confusing, especially for anyone where English is a second language. 

 

"Set Initial Disk Configuration" (or something like it) is still my favorite.

 

Joe L.

 

Seems like the problem is that it is difficult to describe what the restore button does in just one or two words.  Perhaps it would be a good idea for this button to redirect to a screen that says something like ***WARNING*** [a short paragraph describing what's really going to happen] Are you sure you want to do this? Y/N

 

 

Check out this thread (starting at the message posted).  There was a good dialog about renaming the button.  Tom got involved.  Obviously no action.

 

I think Tom gets some sadistic pleasure out of seeing how many different ways Joe L. can explain how bad the restore button's name is.   

 

THREAD LINK

 

 

 

Seems like the problem is that it is difficult to describe what the restore button does in just one or two words.  Perhaps it would be a good idea for this button to redirect to a screen that says something like ***WARNING*** [a short paragraph describing what's really going to happen] Are you sure you want to do this? Y/N

 

 

I agree... It needs a page exactly as you describe... Are you sure?  Are you sure you're sure? Are you certain you're sure you're sure?

 

Funny (not humorous, but interesting) thing is, from what I learned today, it appears as if the button is NOT needed at all, ever.   It seems to be exactly equivalent to deleting the super.dat file on the flash drive.  (Something a new user to unRAID is far less likely to do in a panic when they are trying to restore a failed drive.)

 

To be fair, the original versions of unRAID used a hidden second partition on the flash drive to store the superblock.  It was not even a file-system with a system.dat file, just a collection of bits in the partition. Tom only sold the flash drives pre-loaded, so to make it easier, it was needed then, to permit somebody to deal with the second hidden partition.  Back then, the restore button had a true purpose.  Today... If we cannot come up with a good label for it... I'd lobby to lose it to history.

 

If you ever delete a disk from your array permanently, how hard is it to add one or two lines to the manual that says something like: 

Delete the config/system.dat file and re-start the array to force the unRAID server to save a new array configuration based on your currently assigned and working drives.

 

Joe L.

 

 

good idea....

 

 

NO ONE should press restoire without fully understanding what it does. As has been said many times, it does NOT help restore data from a failed disk.  But ...

 

Pressing the restore button at the wrong time is not QUITE as deadly as we once thought.  Using the recently described command (mdcmd set invalidslot <nn>) there are ways to recover in some circumstances.  I will try to write this up in a wki.

 

What IS DEADLY is pressing restore and then starting the array after you have had a drive failure.

 

So if you DO press restore by accident, DO NOT START THE ARRAY.  Ask for help on these forums (at least until a wiki appears that explains your options).

 

Until then it's the second "r" word removed from my vocabulary, along with retirement...