Windows 8 and 8.1 Forums


Storage Spaces Capacity (RAID5)

  1. #1


    Posts : 3
    Windows 8 Pro

    Storage Spaces Capacity (RAID5)


    Hi everyone, I've been using storage space for around a year with pool and raid functionality and I just realized the numbers don't add up... I have 7x 2TB all parts of a single pool with parity. Now here's the numbers:

    Physical space: 14tb
    Storage Space size (user set): 12tb
    Used Storage Space size (according to windows explorer): ~6tb
    Used Storage Space size (according to storage spaces): ~9tb
    Individual drive used % (according to storage spaces): ~75% each

    Storage spaces tells me to add a drive, low capacity... So I know how normal RAID5 works and it really shouldn't use 50% of the total used space as shown by the numbers above (6tb + 3tb assumed to be parity = 9tb). Also, if I need to add another drive, this means I'm almost full at 6tb/14tb?! This is worst than MIRROR RAID...

    Am I reading it wrong?

      My System SpecsSystem Spec

  2. #2


    Posts : 1,925
    Windows 8.1 Pro


    Storage Spaces is not RAID5.

    It is more akin to the old PAR archive system they used to use for transferring binaries over usenet. You can also over-commit. That is, you can define more disk space than you actually have, and then just add more drives as you increase space.
      My System SpecsSystem Spec

  3. #3


    Posts : 3
    Windows 8 Pro


    Sorry if my question was not precise enough. "Why is windows 8 storage spaces taking more than 100% of total used data size for parity? (Making it less space efficient and of course less reliable than mirror raid).

    I know I can increase the total pool size and add more drives, I'm just wondering why on a 14tb pool with parity I get to use only ~6tb. It doesn't make any sense, how can parity use up more space than a mirror?!
      My System SpecsSystem Spec

  4. #4


    Posts : 1,925
    Windows 8.1 Pro


    Parity drives are not the same as Mirror drives, and they have different benefits and different issues. StorageSpaces major benefit is that you can drop in new drives without resizing partitions.

    You may find this discussion helpful. Confused on Storage Spaces with Parity and free space
      My System SpecsSystem Spec

  5. #5


    Posts : 3
    Windows 8 Pro


    Yes! That thread answers exactly my question, thank you!
      My System SpecsSystem Spec

Storage Spaces Capacity (RAID5)
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