Share via

Creating a storage pool and virtual disk

Jim Paige 110 Reputation points
2026-05-14T21:52:50.3133333+00:00

I have a script from another member that will create a storage pool and then the virtual disk
It has variables in it for AllocationUnitSize and Interleave. The original values were 8192kb AUS and 512kb Interleave.

After running the script, I observed the transfer speed to that pool running at ~200MB/s. However after a little while the transfer speed dropped to zero, and the disk activity Leds on all 4 drives in the pool keep flashing for up to 2 minutes. I assume this because the transfer is waiting for the write cache to be committed to the disks. The Led lights eventually are on solid, but the transfer is still hanging. Eventually after quite a while the transfer will pick up again and run at an acceptable speed. But at this point the transfer hangs almost immediately and i have to close the transfer screen. When I try to delete the file in process it says the file is still in use (by one of the explorer processes). It will eventually release that file and complete the delete of the file. So I reload the two explorer screens and navigate to the folders I was in and started another Windows copy process instead. After starting another Windows explorer copy , I have to pause it immediately as the destination pool led lights start flashing again like it was dumping the cache but there shouldn't be much in the cache as I JUST started the transfer.

I am not sure what is going on but it kind of reeks of the way that virtual drive is created.

I have tried rebuilding the virtual drives with different combinations of AUS and Interleave with not much success.

Anything could help. I am using that storage pool as a backup for the over 25,000 multimedia and music files I have on my main single HDD. But the copy exhibits the behavior even when I copy only one file. The larger the files, the more often the transfer hangs.

Do any of you with more experience designing a storage pool have any advice?

Anything could help.

Thanks!

Windows for home | Windows 11 | Files, folders, and storage
0 comments

Answer accepted by question author

AI answer

2026-05-14T21:53:21.7966667+00:00

Storage Spaces performance and eligibility are tightly coupled to how the pool and virtual disk are created, but the context only provides supported, documented knobs and error conditions, not specific tuning values for AllocationUnitSize and Interleave for a given workload.

From the available information:

  • Storage Spaces virtual disks are created from a storage pool, and their layout and provisioning type (thin vs fixed) directly affect performance and behavior during large copies. When creating a virtual disk, the wizard (or equivalent API) requires choosing a storage layout (simple, mirror, parity) and provisioning type, and warns if there are not enough disks for the chosen layout.
  • The MSFT_StoragePool.CreateVirtualDisk method supports parameters such as Interleave, NumberOfColumns, NumberOfDataCopies, and PhysicalDiskRedundancy. These override defaults from the resiliency setting. If any of these are out of range or not supported by the pool, the operation returns an error. Interleave * NumberOfColumns defines the stripe size, which is a key performance characteristic.
  • The storage pool’s resiliency settings and defaults (including InterleaveDefault, NumberOfColumnsDefault, etc.) are what should normally be used unless there is a specific, documented reason to override them. Overriding them with unsupported or suboptimal values can lead to poor performance or errors.
  • Storage Spaces only uses disks that Windows recognizes as eligible physical disks. Many USB enclosures or hubs present disks as removable or hide multiple disks behind one device identity, which Storage Spaces excludes by design. This can affect both pool composition and performance if the hardware is not presenting disks as standard fixed disks.
  • For drives that cannot be pooled or behave unexpectedly, the CannotPoolReason property on each physical disk (via Get-PhysicalDisk) indicates issues such as “In a pool”, “Not healthy”, “Removable media”, or “In use by cluster”. These conditions must be resolved before reliable operation.

Given the constraints of the context, the supported guidance is:

  1. Ensure all disks in the pool are recognized by Windows as fixed, eligible physical disks (not removable, not behind RAID/"smart" USB enclosures). If they are presented as removable or otherwise ineligible, Storage Spaces behavior is not supported and may be unstable.
  2. Prefer using the default resiliency settings of the storage pool when creating the virtual disk, rather than manually forcing Interleave and related parameters, unless there is a specific, documented requirement. The storage subsystem chooses supported values; out-of-range or unsupported overrides can cause errors or degraded behavior.
  3. Verify that the storage layout and provisioning type match the number of disks and intended workload. For example, mirror layouts require a minimum number of disks; thin provisioning can over-allocate capacity and requires careful monitoring of available space.
  4. If a drive in the pool is unhealthy or misconfigured, use the Storage Spaces tools (PowerShell or Server Manager) to remove or reset it before recreating the pool and virtual disk.

The context does not provide specific recommended AllocationUnitSize and Interleave values for multimedia backup workloads, nor detailed troubleshooting steps for the described intermittent hangs, so only the general, documented behaviors and constraints above can be stated.

References:

AI-generated content may be incorrect. Read our transparency notes for more information.

Was this answer helpful?

1 person found this answer helpful.

1 additional answer

Sort by: Most helpful
Most helpful Newest Oldest
  1. Jim Paige 110 Reputation points
    2026-05-14T21:59:28.82+00:00

    Thank you for this! I will take all that into consideration. But for now I have manually copied many files to the new pool and do not want to delete the pool and use the Windows GUI to create it instead of running that script. I think I tried that already and observed the same behavior. I would gladly trade a slower speed (not ridiculously slow like now) for a stable speed. It would be nice to be able to copy multiple files at once. By the way the virtual drive is Simple and Fixed.

    Was this answer helpful?

Your answer

Answers can be marked as 'Accepted' by the question author and 'Recommended' by moderators, which helps users know the answer solved the author's problem.