On Mon, Dec 12, 2016 at 05:20:21PM -0800, javocado wrote: > Hi, > > I'm setting up a bhyve wherein: > > host # truncate -s 1T vol.file > host # du -ah vol.file > 200K vol.file > > host # /usr/sbin/bhyve ... -s 4,ahci-hd,vol.file ... > > Then inside the bhyve I create a zpool (ada0 = vol.file): > > bhyve # zpool create -O devices=off -O atime=off -O compression=on -m > /mnt/data1 data1 ada0 > > And I put a bunch of stuff in the zpool ... and the vol.file grows in size: > > host # du -ah vol.file > 100G vol.file > > Then I remove the files from the zpool and the zpool usage returns to 0 but > of course the vol.file size does not shrink, the data is still there (but > not referenced?) > > Normally I'd just write zeros to a file inside the zpool until the pool > fills up, then maybe cp --sparse vol.file for good measure, but with > compression on in the zpool the zeroing doesn't really fill up space or > seem to overwrite anything. In my testing the zero file grew larger than > 100G with no change to vol.file I did not let it run forever, however. > > Any other ideas how to scrub off or clear out deleted data from a zpool > and/or this kind of file-backed device?
Instead of dd'ing /dev/zero, try /dev/random. All zeros compress extremely well, [pseudo-]random data does (or, ideally, should) not. -- Shawn Webb Cofounder and Security Engineer HardenedBSD GPG Key ID: 0x6A84658F52456EEE GPG Key Fingerprint: 2ABA B6BD EF6A F486 BE89 3D9E 6A84 658F 5245 6EEE
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