doc: Purpose of a cache pool

Completing the description of the cache purpose.
Fixes : #11096
Signed-off-by: Gael Fenet-Garde <gael.fenet.garde@gmail.com>

diff --git a/doc/dev/cache-pool.rst b/doc/dev/cache-pool.rst
index f44cbd99ac4a8db84bdbee5d1e9a09e5d42fc598..3549ba81dfcd47c9aa0445c892f5acedf47c7f46 100644 (file)
--- a/doc/dev/cache-pool.rst
+++ b/doc/dev/cache-pool.rst
@@ -5,7 +5,7 @@ Purpose
 -------
 
 Use a pool of fast storage devices (probably SSDs) and use it as a
-cache for an existing larger pool.
+cache for an existing slower and larger pool.
 
 Use a replicated pool as a front-end to service most I/O, and destage
 cold data to a separate erasure coded pool that does not currently (and