[dm-devel] [PATCH] dm-cache: document zeroing metadata device step
Austin Chang
austin880625 at gmail.com
Sun Jul 12 19:40:39 UTC 2020
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 at gmail.com>
---
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
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