dm vdo doc: document metadata size

Commit Message

Matthew Sakai March 7, 2024, 10:42 p.m. UTC

Signed-off-by: Matthew Sakai <[e-mail]>
---
 Documentation/admin-guide/device-mapper/vdo.rst | 11 +++++++++++
 1 file changed, 11 insertions(+)

Patch

diff --git a/Documentation/admin-guide/device-mapper/vdo.rst b/Documentation/admin-guide/device-mapper/vdo.rst
index a3572582ead8..7e1ecafdf91e 100644
--- a/Documentation/admin-guide/device-mapper/vdo.rst
+++ b/Documentation/admin-guide/device-mapper/vdo.rst
@@ -34,6 +34,17 @@  The repo also contains additional userspace tools which can be used to
 inspect a vdo target's on-disk metadata. Fortunately, these tools are
 rarely needed except by dm-vdo developers.
 
+Metadata requirements
+=====================
+
+Each vdo volume reserves 3GB of space for metadata, or more depending on
+its configuration. It is helpful to check that the space saved by
+deduplication and compression is not cancelled out by the metadata
+requirements. An estimation of the space saved for a specific dataset can
+be computed with the vdo estimator tool, which is available at:
+
+https://github.com/dm-vdo/vdoestimator/
+
 Target interface
 ================