Microsoft finally fixes Storage Spaces, adds rebalancing command!

Anyone that has used Storage Spaces has probably seen that Storage Spaces does not redistribute files when a new disk is added to the space. Let's say you had a Storage Space with two 1 TB disks. If they filled up and you added a third 1 TB disk, you'd see Storage Spaces using close to 100% disk space on the first two disks and almost 0% on the new disk. The only way to fix this previously was to remove the files from the Storage Space to somewhere else, and put them back in, or hot-remove drives from two/three way mirrors and have them reintroduced. There is even a hefty discussion on the topic on SuperUser.

Not anymore. In Windows 10 and Windows Server 2016, Microsoft have added the Optimize-StoragePool PowerShell command!

Here is how it works. I started out creating a Simple Storage Space (no resiliency) with one 5 GB disk, and added a few files to it, resulting in this.

So, I added a new 10GB disk, and saw the all too familiar uneven space distribution. I even added a few more files after that.

So, I simply fired up PowerShell in administrator mode and issued the Optimize-StoragePool -FriendlyName "Storage pool" command and waited as the command progressed.

And behold, my Storage Space was now optimized/rebalanced! It intelligently rebalances files based on disk space, disk size and file size as far as I can tell, and it's certainly much better than not being able to do it at all.

And just for fun I added a third disk, 15GB in size to and rebalanced again to see what would happen. Here is after adding the third disk and before rebalancing.

And after rebalancing.

This was just a preliminary test of the new Optimize-StoragePool command but so far it seems to work pretty well. I might even switch back to Storage Spaces for my home server once Windows Server 2016 is released. :)

Update - August 25th 2015

After responses from Microsoft employees in the comments below, here are some more details.

• If you set up your storage pool on an earlier Windows version than Windows 10 or Windows Server 2016, make sure you run
  Update-StoragePool -FriendlyName "[NameOfYourStoragePool]" before you try running the rebalancing command. This command should upgrade the metadata for the storage pool to enable new features and functionality.
• The rebalancing command only works on simple and mirrored spaces. It is currently not supported for parity spaces, although that functionality is being evaluated.

Update - June 26th 2018

A long overdue update, and most of you probably know by now, but rebalancing now works on parity spaces as well :)