[linux-lvm] The size specified by "lvcreate -L" is not accurate

Gionatan Danti g.danti at assyoma.it
Thu Sep 2 13:24:00 UTC 2021

Il 2021-09-02 05:26 Yu, Mingli ha scritto:
> Per
> https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git/tree/doc/RelNotes/v1.46.4.txt
> [1], after e2fsprogs upgrades to 1.46.4, the defaults for mke2fs now
> call for 256 byte inodes for all file systems (with the exception of
> file systems for the GNU Hurd, which only supports 128 byte inodes)
> and use "lvcreate -L 50 -n lv_test1 vg_test && mke2fs
> /dev/vg_test/lv_test1" and then continue to check the partiontion as
> below.(use lvm2 2.03.11 for the test)
>  # df -h | grep dev/mapper/vg_test-lv_test1
>  /dev/mapper/vg_test-lv_test1   48M   14K   46M   1% /mnt/lv-test
>  Though claim 50M as above, but it turns out to be only 48M.

I think that allocation are done in multiple of physical extent size 
which, by default, is at 4 MB.
50 is not a multiple of 4 while 48 is, so "lvcreate" probably rounded 
down the required size.
Using one or more "-v" should bring progressively more details.


Danti Gionatan
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