This may be insufficiently useful to justify implementing, but I thought it was an interesting concept. One of the current issues with dm-crypt and discard is that enabling it can leak information about the filesystem and usage patterns of the disk[1]. If a dm-thin device with a random block placement strategy is layered on top of dm-crypt however, this could solve some of the issues involved and partially mitigate others. Such a random block placement strategy would heavily disguise any layout patterns that could be used to identify the filesystem, most likely to the point of being completely unrecognizable. Issues arising from discarded blocks being nonzero are avoided by default due to dm-thin pre-zeroing allocations (unless skip_block_zeroing is enabled). However, some issues would still be present: While the *distribution* of unused sectors would be concealed, their existence and how many there are would still be detectable. In addition, the issues with trim and a hidden device are still present. [1] http://asalor.blogspot.com/2011/08/trim-dm-crypt-problems.html -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
