Hi all,

so my first server was setup with the drives being filled with the share setting of High-Water. After having that server set like that for close to a year I would like to have the data more evenly distributed across the server. Is there a way to do this on an existing server without moving all the data off the server and back on again?

Thanks for any help

You might find this thread to be of interest.

There's no real reason to bother with moving data around.    If you'd like the disks to become more uniformly full as time goes on, just change your setting to "Most Free" -- and over time they'll be uniformly filled.

 

Well the reason I was thinking about this is due to my old server has the first 5 drives sitting close to 95% full and the new drives are barely used. From a failure perspective my thoughts are that if the data were more evenly spanned across all the disks, then it would make a disk issue less painful as it would not be totally full disks that would be lost.

As a side note, this server is now becoming the backup server and my newly assembled server will become the main server once I finish copying across 18tb of data.

That's the whole point of the parity disk, it provides fault tolerance for a failed disk. I'm not sure if it matters, though, if a disk is 1% full or 100% full when it comes time to rebuild it - since you're not doing a file-by-file restore, but a whole disk rebuild, I wouldn't think it matters.

 

Maybe someone with more expertise or unfortunate experience can chime in.

Well I am more thinking if 2 drives fail

without backups, you're hosed either way with a 2 drive failure...

Hence my point, the loss would not be as great if both drives had the data shared between them. But as I indicated in the thread earlier, I have a second unRAID server which I built as a backup to the first machine

I am actually also interested in this, perhaps a feature request?

 

Scenario, let's say I have four 4TB disks and each has 250GB free.  I add two more 4TB disks -- would be awesome to be able to tell unraid to re-allocate the data evenly across all drives, spreading the data out again.

 

Add another drive, spread the data out again.  Rinse and repeat.

 

 

Exactly what I am trying to do. :-)

If you're concerned about data loss, you should be sure you have good backups -- not about whether your data is spread evenly across the array disks.

 

If, however, you want the data spread evenly, you can, as I noted earlier, just set the allocation to "Most Free" -- and then all disks will eventually have about the same amount of free space.    You can, if you want, move data around on your UnRAID disks, but if you do so, be CERTAIN that you copy from disk shares to disk shares -- NOT through the User share mechanism, as there's a "bug" that will cause major data loss in that case.

 

In this specific case, since you're going to keep the old server for backups (a good idea), if you simply want the data evenly distributed on your new server, just set the allocation method as I noted above and when you copy the data to the new server it will automatically be uniformly distributed.

 

Evening out the data adds no additional safety. It's far more important to have inventory of the disks contents and manintaining the inventory is greatly simplified if disks are filled one at a time and then left unchanged.

 

My simple array has 2 data disks and either disk may fail with an even probability.  If both disks are 50% full (.5data), loosing 1 disk means I loose 50% of my data. If one disk is full, (1data), and one is empty, (0data), and either may fail the percentage of data I will loose is still 50% on average. Generalizing this to include multiple disks and parity does not change the conclusion.

 

Case 1:  .5 x.5data + .5 x .5data = .5data

Case 2:  .5 x 0data + .5 x 1data = .5data

 

Spreading the data has no benefit relative to data lose and makes data management more complicated. Fill the disks one at a time and maintain inventory and checksums with the time you'll be saving.

Evening out the data adds no additional safety. It's far more important to have inventory of the disks contents and manintaining the inventory is greatly simplified if disks are filled one at a time and then left unchanged.

 

My simple array has 2 data disks and either disk may fail with an even probability.  If both disks are 50% full (.5data), loosing 1 disk means I loose 50% of my data. If one disk is full, (1data), and one is empty, (0data), and either may fail the percentage of data I will loose is still 50% on average. Generalizing this to include multiple disks and parity does not change the conclusion.

 

Case 1:  .5 x.5data + .5 x .5data = .5data

Case 2:  .5 x 0data + .5 x 1data = .5data

 

Spreading the data has no benefit relative to data lose and makes data management more complicated. Fill the disks one at a time and maintain inventory and checksums with the time you'll be saving.

 

You are correct there with the law of averages.  Personally whenever I add a new hard drive, I always balance out the media on them.  My rationale is that if 2-3 new movies are being watched concurrently, the odds are that with my share settings set to most-free, there will be less thrashing of the heads, since most likely the movies will be on different drives.