Date: Thu, 20 Apr 2017 02:39:12 -0700 From: Maxim Sobolev <sobomax@freebsd.org> To: FreeBSD Filesystems <freebsd-fs@freebsd.org>, Kirk McKusick <mckusick@mckusick.com> Subject: UFS snapshot "file" is slightly bigger than underlying disk partition Message-ID: <CAH7qZfs4oBdtvJEir95eHkTeVm%2BTPO59%2Bz2L1n0pXj4o3fB9Ww@mail.gmail.com>
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Hi Kirk, I've noticed that the snapshot file is slightly bigger than underlying disk partition. First I thought it's some kind of header attached to the end, but the size of difference is actually dependent on the disk size. Is it by design, or some sort of "off by x" error? What's annoying about that is that the size is not multiple of SECTOR_SIZE. Also looks like if I just cut that junk out resulting FS image is just as usable. Attached script illustrates that. The first column is size of the partition, the second column is the size of the difference, both in bytes. 1048576 48 2097152 56 4194304 72 8388608 72 16777216 72 33554432 72 67108864 72 134217728 72 268435456 72 536870912 72 1073741824 72 2147483648 72 4294967296 96 8589934592 152 17179869184 256 34359738368 464 68719476736 880 137438953472 1720 274877906944 3392 549755813888 6744 Please advise, thanks. -Max (P.S. This is 11.0-RELEASE-p9)
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