Disk space lost with partitioning (windows 10 - disk management)

Question

It is the second time (since a long time ago) i try on my computer to create a small partition, using the default windows 10 disk management tool. First step is to shrink my C drive, and windows asks me how much i want to shrink it: i put the bare minimum, i.e. 1 MB only. Again, as the first time i tried it long ago, after the process the disk management only shows the original C partition, with 1 MB less of space available, but there is no trace of the new small partition it should have been created. I also ran Partition Magic in order to recover lost partitions, but it did not find anything. I really do not know why this happens, and how to get back my lost space. Thank you for your help!

edit:As answerers said, that unallocated space was to small to even show up. I then proceeded to shrink my C: drive again, this time by 548 MB, and now i finally see again those 2 "lost" MB in the unallocated section. Cool, but when i try to extend my C: volume back to what it was at the beginning, the maximum amount allowed it 548 MB, not 550. It seems like i cannot touch those 2 MB, even if they are actually showing up now. Pic: dropbox.com/s/sm4qrgpos1vcg0d/Senzanome.png?dl=0

Answer 1

You have three times reduced the partition, by 1 MB, again by 1 MB, then by 548 MB. The problem is that Disk Management only allows to re-grow the disk by 548 MB.

This space is not lost, since it is well-indicated in Disk Management when doing right-click of "Disk 0" followed by Properties, as the Volumes tab reports "Unallocated space" as being 3 MB (which is one more than it should be).

My own experience is the same: My system disk was originally fully allocated to the maximum size given by Disk Management, yet "Unallocated space" is reported as 2 MB. Unlike you, I don't have the least idea where on the disk is this unallocated space, but I would guess it is to be found at the end of the disk.

My inescapable conclusion is that Disk Management rounds-down the space. This means that it is calculating disk space in units larger than one MB, truncating numbers to this unit-size.

I am unaware of any information on the internals of Disk Management, so cannot go further than that supposition.

I remark that this idiosyncrasy of Disk Management is good to know. It means that when resizing partitions, one runs the risk of losing a few MBs of space here and there (which is not much, considering the size of modern disks).

You could report this problem to Microsoft via the Feedback Hub, in the (small) hope of getting an explanation. I don't think that this space can be retrieved without re-partitioning the entire disk, which is not worth it for only 3 MB.

Answer 2

There is no lost partition, because shrinking a partition does not automatically create a new one. You get some unallocated space and it's up to you to partition it further, e.g. by selecting "Create new simple volume" in Disk Management.

However, 1 MB is far too small to create a useful partition. I mean, it's not impossible (e.g. by formatting it as FAT12 like a 3.5" floppy disk), but it's impractical and many partitioning tools simply don't show unallocated gaps that small, often under the assumption that the gap is there because of MBR logical partitions, or because of old-style CHS alignment, etc. It varies between programs.

Try shrinking the existing partition a bit more, to create at least 20–50 MB of space (or even 200–500 MB to make it kinda useful); then the "Unallocated" section should show up and you'll be able to create new partitions in that space.

(Alternatively, to just recover the space, grow your C: partition back by 1 MB.)

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Also note that some tools which recover "lost" partitions do so based on their expected contents: i.e. they look for typical FAT32 or NTFS headers, and if they find one, they assume it's the start location of where a partition might have been. But because of that, completely blank (not yet formatted) partitions cannot be found using such tools – because they didn't contain anything to find.

Answer 3

There are several issues here. Resizing a partition does not create a new partition. All you accomplished was reducicg the size of the existing partition by 1 MB. Any free space would be unallocated space after that partition. When a drive has unallocated space, you can select it to create a new volume. However, 1 MB is not enough space to create a new volume. It would appear that the minimum space to create a new volume appears to be 8 MB. The only reference I could find to the minimum size of a NTFS volume was quite old, so that might not be accurate anymore. That being said, you should try reducing the existing volume by more, then you should see unallocated space after.