Multi-drive pools must currently use btrfs or ZFS.

[Jaybau]

1. How does Unraid use BTRFS/ZFS for non-array multi-drive pools?
2. Why BTRFS/ZFS?
3. Why doesn't Unraid use XFS for non-array multi-drive pools?
4. Should Unraid allow XFS for single-drive pools?  But then later if you want to add another drive to the pool, you can't, and you'll have to format the XFS drive and do multiple file transfers.  I would rather not have an option for XFS for pools, and avoid this problem.  If a user wants to use XFS, they can use the Unassigned Drive feature of Unraid.

[itimpi]

5 minutes ago, Jaybau said:

1. How does Unraid use BTRFS/ZFS for non-array multi-drive pools?
2. Why BTRFS/ZFS?
3. Why doesn't Unraid use XFS for non-array multi-drive pools?
4. Should Unraid allow XFS for single-drive pools?  But then later if you want to add another drive to the pool, you can't, and you'll have to format the XFS drive and do multiple file transfers.  I would rather not have an option for XFS for pools, and avoid this problem.  If a user wants to use XFS, they can use the Unassigned Drive feature of Unraid.

Btrfs and zfs natively support multi-drive pools - xfs does not.

 

xfs is deemed to be faster and more tolerant of faults at the hardware level which is why it is kept for single drive pools.

 

[Jaybau]

In Unraid, I thought each drive was independent, and physically separated in the OS, but just "virtually" pooled to represent a single storage mount.

[itimpi]

10 minutes ago, Jaybau said:

In Unraid, I thought each drive was independent, and physically separated in the OS, but just "virtually" pooled to represent a single storage mount.

In the main Unraid array that is true - not in pools (at least the current btrfs and zfs ones) where the file system handles the multi-drive aspect without help from Unraid and provides a single mount point for the whole pool.

 

[Jaybau]

Note: Just realized Unraid ZFS cannot add another drive and expand the pool later.

 

Quote

Additional flexibility in adding/expanding vdevs will be provided in a future update.

 

What I did is created a few unassigned drives, formatted with ZFS, did the data shuffle, and wanted to pool them together via Unraid.  But if I do that, I presume it creates a ZFS pool, not a proprietary Unraid pool, therefore has the limits of ZFS (or Unraid's current implementation of ZFS).

 

So I'm going with BTRFS so I can expand and/or take out drives later.

 

 

[Jaybau]

Ran into this problem:

 

I noticed my BTRFS pool is not 2 TB, but 1.5 TB.

 

The pool is configured with the File system type = BTRFS; Single:

 

I noticed some unexpected info regarding RAID1:

 

Special/important notes:

I originally created the pool as "single", but it looked like unraid created it as a radi1 mirror.  So I cancelled the operation, and have been attempting to redo the configuration without success.

 

There was some other strange behaviors too:

1)  Originally it was 1TB total combine space.  So I attempted to "balance" to a "single" drive, even though I originally selected "single".

2) Drives can no longer be removed from the pool and mounted.

 

I have another pool created months ago.  I didn't have this problem/steps/scenario.  The "df" looks different too:

I'm getting into the weeds on this.  I'm attempting to run a "balance to single" (I don't know if I need to do a "full balance," or what that will do, but might have to try it), and hope I get back to the point where I have 2 independent BTRFS drives that I can take out of the pool and mount as unassigned (just like the older created pool from months ago). <-- This seems to be an incorrect assumption made by me.  Once the drives are in an Unraid pool, they become part of the filesystem, and no longer separate independent drives.

tower-diagnostics-20240107-1554.zip

Edited January 8 by Jaybau

[Jaybau]

The system completed the balance convert to single mode:

 

I expect the combined size of the two disks to be 2 TB.

But from the screenshot, I have 3TB (not 2TB) !

[JorgeB]

Please post the current diagnostics.

[Jaybau]

I resolved the incorrect total pool size by restarting the array.

I have one diagnostic report in the previous post. 

I include one here too.  There might be a time gap between the logs since I restarted the array between the issues.

Thank you.

tower-diagnostics-20240108-0901.zip

[JorgeB]

If it looks good now not much to see.

[Jaybau]

Has there been discussion to use a union file system for Unraid multi-drive pools?

 

I have some old drives that I wanted pooled together.  I don't want them in the array.  Some of the drives would be temporarily added to the pool.  I want to pool the drives into a single virtual/merge/union file system pool.  Basically like the Unraid array, but without the parity.

 

Does Unraid have this capability (non-array, no parity)?

[JorgeB]

7 minutes ago, Jaybau said:

Has there been discussion to use a union file system for Unraid multi-drive pools?

Not that I know of.

[Drew6274]

55 minutes ago, Jaybau said:

Has there been discussion to use a union file system for Unraid multi-drive pools?

 

I have some old drives that I wanted pooled together.  I don't want them in the array.  Some of the drives would be temporarily added to the pool.  I want to pool the drives into a single virtual/merge/union file system pool.  Basically like the Unraid array, but without the parity.

 

Does Unraid have this capability (non-array, no parity)?

 

 

There is a mergerfs plugin for unraid. 

 

[Jaybau]

Thanks, I'll take a look at the plugin. 

 

I proposed a native feature for consideration: