| Message ID | 20200712194039.329035-1-austin880625@gmail.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
| Series | dm-cache: document zeroing metadata device step | expand |
On Sun, Jul 12, 2020 at 08:59:32PM +0100, Matthew Wilcox wrote: > On Mon, Jul 13, 2020 at 03:40:39AM +0800, Austin Chang wrote: > > + # 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 > > ... don't you need 'count=1' or you'll zero the entire device? Oops, I copied the command I just used since zeroing the whole metadata device didn't harm. But 'count=1' should match what I've just written. I will send a v2 patch later -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
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 \
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@gmail.com> --- Documentation/admin-guide/device-mapper/cache.rst | 4 ++++ 1 file changed, 4 insertions(+)