Inform dmsetup users to zero the first 4k of the metadata device at cache creation in examples, just as mentioned in thin-provisioning documentation. Instructions to use lvmcache for end users may be added as well. Link: https://www.redhat.com/archives/dm-devel/2013-April/msg00124.html Signed-off-by: Austin Chang <austin880625@xxxxxxxxx> --- Documentation/admin-guide/device-mapper/cache.rst | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Documentation/admin-guide/device-mapper/cache.rst b/Documentation/admin-guide/device-mapper/cache.rst index f15e5254d05b..ef9a82d50d19 100644 --- a/Documentation/admin-guide/device-mapper/cache.rst +++ b/Documentation/admin-guide/device-mapper/cache.rst @@ -330,6 +330,10 @@ https://github.com/jthornber/device-mapper-test-suite :: + # When using dmsetup directly instead of volume manager like lvm2, + # the first 4k of the metadata device should be zeroed to indicate + # empty metadata. + dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ /dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0' dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \ -- 2.26.2
