When there's unused space on my UnRaid server, I may wish to move one or more drives somewhere else. The manual says:

 

"Remove one or more data disks:

In this case the missing disk(s) will be identified. If there is only one missing disk when you start the array it will be marked as failed. All data disks will be exported (including the missing one), but the system will be running unprotected; that is, if a disk fails you will lose data."

 

Does this mean that when we remove the drive from the array, the array is unprotected during the removal process? Can't the server recognize that the drive hasn't failed and simply copy the content and let it remain protected?

When there's unused space on my UnRaid server, I may wish to move one or more drives somewhere else. The manual says:

 

"Remove one or more data disks:

In this case the missing disk(s) will be identified. If there is only one missing disk when you start the array it will be marked as failed. All data disks will be exported (including the missing one), but the system will be running unprotected; that is, if a disk fails you will lose data."

 

Does this mean that when we remove the drive from the array, the array is unprotected during the removal process? Can't the server recognize that the drive hasn't failed and simply copy the content and let it remain protected?

if any drive is removed, or disabled, the array is un-protected from a subsequent failure.  Basically, the single removed drive is simulated.  (You can still read and write to it)  You should replace it as soon as practical.

 

The array never moves data from one data drive to another.

 

Joe L.

So that means if the user can not leave the array unprotected at any time, he can not simply remove the disk in the interface. I know in the old Windows Home Server the server can safely remove a drive from the pool by copying data from the drive to be removed to the pool first before its removal, so this seems to be a matter of implementation, and just happens to be unavailable in this case.

You can copy the data yourself and then remove the drive and tell unRAID to rebuild the parity without that drive. You will be unprotected until the parity is built again.

 

 

That still exposes the other drives in the array during the rebuilding though.

 

I'm thinking, if you power down the server, manually clone the parity drive to another drive (say, the drive to be marked as removed, assuming they're the same size), then do the rebuild. If a drive fails at this time, you'd still have a backup of the parity drive. I don't know if this would work in practice though, since any change in the data drives would change the state of the parity. If the data drives were write-protected in this process I think it would work.

Unless ofcourse your parity drive fails during the clone and during bootup of the system you loose another drive...

 

Basically there is always the possibility of drive loss..  With unraid the issue is smaller then with RAID5 since you will only loose the drive that goes bad, rest of the array will still be readable..

 

It all depends on what kind of data you do not want to loose... If double drive failure (which is unlikely) is something you want to guard yourself against then you probably also need protection from burglars (what if they steel your system), and glasses of coke falling into the server... Both would point you to an extra layer of security consisting of data backup OUTSIDE of the array and located at another location... Personally I do that with my familiy photo's and documents, copy them to a spare drive every once and so often and put in the cupboard with my parents..

You can zero the drive to be removed. Then, the parity is the same with or without it.

There is a walk through of the procedure to do this here:

 

http://lime-technology.com/forum/index.php?topic=2591.msg20919#msg20919

 

One would think that this would be a useful thing to add proper support for so that it is easy to do; however, this might be one of those features that really is not that useful.  I thought I might want to do this a couple of times in the past, but each time I just ended up buying a bigger disk and replacing the "unused disk" with something bigger.

 

Regards,

 

Stephen

Personally I do that with my family photo's and documents, copy them to a spare drive every once and so often and put in the cupboard with my parents..

You put your parents in the cupboard?

 

Don't they complain about having to share the space with your backup disks? 8)

 

Joe L.

I am sure it's a big enough cupboard.

 

(I had exactly the same vision, Joe.)

I am sure it's a big enough cupboard.

 

(I had exactly the same vision, Joe.)

Hey hey hey, let's not be insensitive. Maybe his parents are in urns.

Unless ofcourse your parity drive fails during the clone and during bootup of the system you loose another drive...

 

Yeah but that's assuming a two drive failure, whereas in the current situation a single drive failure would lead to data loss while the parity drive is being rebuilt when you simply remove any drive, even a healthy one.

 

An example of a safer implementation for removing a healthy data drive is a combination of what lionelhutz said:

1) copy data on the drive to the array, provided there's sufficient free space (now there are two copies of the drive's data). Update the parity.

2) Zero the drive. Write-protect the array then update the parity again.

3) Remove the drive from the pool without changing the parity. Release write-protection.

 

Here, single drive protection is maintained at all times, which makes the process less risky, and no extra space is required.

 

The safe thing to do in Unraid for now seems to be to avoid removing drives whenever possible.

 

Separate back ups are always important, that's a given.

Personally I do that with my family photo's and documents, copy them to a spare drive every once and so often and put in the cupboard with my parents..

You put your parents in the cupboard?

 

Don't they complain about having to share the space with your backup disks? 8)

 

Joe L.

 

Jup, big glass pane upfront and a hammer next to it "Break in case of emergency"  :-)