Expand Windows 10 Storage Spaces pool by replacing drives with larger ones

Question

I have a two disk two-way mirror storage pool. It consists of two 2TB drives. It's at about 75% capacity and the drives are somewhat old. I'd like to replace the drives and expand the array. To be clear, what I want to do is end up with the same storage pool with two mirrored 4TB drives. The drives are internal in a tower desktop enclosure and I'd like to end up with the same arrangement. I've read this question and it seems on-point but it refers to a parity based pool.

The technique described would is:

1. Add one new 4T drive on USB and add to the pool.
2. Prepare one of the original 2T drives for removal.
3. Remove the 2T drive and replace it with the second 4T drive.
4. Prepare the other 2T drive for removal. All data should now be on the 4T drives.
5. Remove the second 2T drive and move the first 4T drive from USB to the internal SATA port.

The other question and the docs refer to preparing an existing drive for removal. On my computer, in the physical drive section of the Manage Storage Spaces there is no option for preparing the drive for removal, only "rename". Is it possible to use the described procedure in a mirror situation? Is there another way to accomplish what I want to do?

> PS C:\Users\Elton> Get-PhysicalDisk -FriendlyName PhysicalDisk1 | Get-VirtualDisk
PS C:\Users\Elton> Get-PhysicalDisk

DeviceId FriendlyName            SerialNumber         MediaType   CanPool OperationalStatus HealthStatus Usage       Si
                                                                                                                     ze
-------- ------------            ------------         ---------   ------- ----------------- ------------ -----       --
1        M4-CT256M4SSD1          00000000123709162E33 SSD         False   OK                Healthy      Auto-Select GB
2        Hitachi HDS5C3030BLE630 MCE9215Q0AS51W       HDD         False   OK                Healthy      Auto-Select TB
7        Seagate Backup+  Desk   NA7D0SNK             Unspecified False   OK                Healthy      Auto-Select TB
6        Seagate BUP Slim BL     NA7JAD6P             Unspecified False   OK                Healthy      Auto-Select TB
0        SanDisk SDSSDP128G      131060400181         SSD         False   OK                Healthy      Auto-Select GB
3        TOSHIBA DT01ACA200      23KMRZLAS            Unspecified False   OK                Healthy      Auto-Select TB
4        TOSHIBA DT01ACA200      23JJYEGYS            Unspecified False   OK                Healthy      Auto-Select TB

Answer 1

I'm aware the thread is a few years old, but this page popped up in a Storage Spaces related google search, so I guess it's not buried that deep yet.

To be frank, the proposed approach is silly. You shouldn't, let alone have to, treat a Storage Space like a hardware Raid array. You don't swap and re-build disk by disk with Storage Spaces. (not that you would with an actual Raid array either, if you can avoid it)

Also, those existing 2TB HDDs, though old, had proven themselves to be reliable. The new drives on the other hand could've come from a bad batch. You should always test new drives before you decommission old ones that haven't failed yet. That's one of the nice aspects of software raid, drive pools and virtual disks ... you can easily add new HDDs to the pool and test them without much work or risk. After a month or so, when you're convinced that the new disks won't die any time soon, you prep the old ones for removal from the pool - let Windows move the data around until all Storage Spaces reside entirely on the new disks - then unplug them.

And unless there's not enough physical space, there's no reason to get rid of HDDs simply because they're old. If they're muuuch slower than the new ones, or maybe SMART data shows that they are reallocating sectors at an increasing rate ... ok, throw them out. Otherwise they can provide additional redundancy and emergency capacity for your storage pool. If you don't want old drives to potentially drag performance down, there's also the option to create smaller Storage Spaces and configure the old HDDs as hot spares/ rebuild volumes. Or you create 3-way mirrors. With the OP's 2x 4TB and 2x 2TB disks one could configure two 2TB 3-way mirrored S.Spaces. When it comes to read performance the old HDDs wouldn't make a difference. The request for a certain data block is sent to all drives in the array and the one that finds it first sends the data.

Answer 2

The Storage Spaces Frequently Asked Questions (FAQ) and especially the section How do I replace a physical disk? makes it clear that in order to replace a disk you need the following:

• The storage space must be resilient and healthy (not a simple space). Running the following command should find that ResiliencySettingName is either Mirror or Parity and HealthStatus is Healthy:

  Get-PhysicalDisk -FriendlyName PhysicalDisk1 | Get-VirtualDisk
  

• There is enough space on the other disk to contain the data on the replaced disk. If there isn't enough space, you need to add a new disk before retiring that disk, even just a temporary external USB disk (but this will be slow). You can check unused disks capacity by subtracting AllocatedSize from Size reported by the Get-PhysicalDisk command.

In your case, apparently the above two conditions are not fulfilled, so "Prepare for removal" is not available.

For more information about removing a drive, with screenshots, see:
How to Remove Drive from Storage Pool for Storage Spaces in Windows 10.