Date: Sun, 15 Oct 2023 07:17:57 -0700 From: Alan Somers <asomers@freebsd.org> To: freebsd-hackers@freebsd.org Subject: Re: zpool geli encryption question Message-ID: <CAOtMX2jAs9%2BM79N-4LC9EdZ3y4jbvhWEWCs9KFxL9r=6zt%2BwZw@mail.gmail.com> In-Reply-To: <ZSvrhL3IV4642-n5@int21h> References: <ZSvrhL3IV4642-n5@int21h>
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On Sun, Oct 15, 2023 at 6:39=E2=80=AFAM void <void@f-m.fm> wrote: > > A machine periodically backs up bhyve volume-backed VMs like so: > > # zfs send ssdzfs/fbsd140R | gzip -c > /vol-backups/$(date '+%G.%m.%d_%H:= %M').fbsd140R.gz > > This vm is zfs internally with geli encryption of both the fs and swap. > > The same backup routine applies to an openbsd vm. It has its own way of > filesystem encryption. > > Both volumes are 64GB in size. On the host, both volumes use lz4. > > Surprisingly (to me at least), the freebsd backup results in a smaller > size of archive. The openbsd one results in a slightly larger archive tha= n > its source. > > I'm expecting both archives to be slightly larger than their sources, > because encrypted data is uncompressible. > > The freebsd archive is 19GB. The openbsd one is 65GB. Why is this? How much of the FreeBSD VM's disk is actually in-use? Maybe you are using TRIM with FreeBSD, which punches holes in the host's ZFS storage. That would explain why compression seems to save space, even though the data is encrypted. -Alan
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