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FAQ - Unduplicated vs Duplicated vs Other vs Unusable



The "Other" and "Unusable" sizes displayed in the DrivePool GUI are often a source of confusion for new users. Please feel free to use this topic to ask questions about them if the following explanation doesn't help.
Unduplicated: the total size of the files in your pool that aren't duplicated (i.e. exists on only one disk in the pool). If you think this should be zero and it isn't, check whether you have folder duplication turned off for one or more of your folders (e.g. in version 2.x, via Pool Options -> File Protection -> Folder Duplication).

Duplicated: the total size of the files in your pool that are duplicated (i.e. kept on more than one disk in the pool; a 3GB file on two disks is counted as 6GB of duplicated space in the pool, since that's how much is "used up").
Other: the total size of the files that are on your pooled disks but not in your pool and all the standard filesystem metadata and overhead that takes up space on a formatted drive. For example, the hidden protected system folder "System Volume Information" created by Windows will report a size of zero even if you are using an Administrator account, despite possibly being many gigabytes in size (at least if you are using the built-in Explorer; other apps such as JAM's TreeSize may show the correct amount).
Unusable for duplication: the amount of space that can't be used to duplicate your files, because of a combination of the different sizes of your pooled drives, the different sizes of your files in the pool and the space consumed by the "Other" stuff. DrivePool minimises this as best it can, based on the settings and priorities of your Balancers.


More in-depth explanations can also be found elsewhere in the forums and on the Covecube blog at http://blog.covecube.com/

Details about "Other" space, as well as the bar graphs for the drives, are discussed here: http://blog.covecube.com/2013/05/stablebit-drivepool-2-0-0-230-beta/

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To clarify (and make it simple to find), here is Alex's official definition of that "Other" space:

And then there's "Other". "Other" always confuses people, but it literally is everything else.
So what else is there?

  • Non-pooled files that exist on that disk. Remember that just because a disk is part of the pool doesn't mean that you can't continue to use that disk to store non-pooled files.
  • NTFS Metadata. For every file on a NTFS volume, there is additional metadata associated with that data stream, like the file name, file attributes, modification times, etc. These typically take very little disk space, but can add up if you have lots of files.
  • Directory entries. On NTFS, directory entries are actually stored as regular files with a "directory" attribute. But instead of a data stream, they contain a little database of index entries for each file (and subdirectory) that exists under them.
  • Slack space. Just because you have a 100GB volume, doesn't mean that you can use all 100 Gigabytes of that volume to store data. NTFS divides your volume into equally sized chunks called clusters, which are typically 4096 bytes in size. If your file doesn't fit neatly into these clusters then there's going to be some space at the end of the file that's wasted. We call this "slack space".
    For example, if you have a 2kb text file, it's going to use the full 4kb cluster, even if 2kb is empty space. Same goes with larger files that don't fill that last cluster, which is very common.
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