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-rw-r--r--Documentation/admin-guide/device-mapper/vdo.rst11
1 files changed, 11 insertions, 0 deletions
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
================