doc/rados: reword part of cache-tiering.rst

Reword part of cache-tiering.rst to make the English language added in
https://github.com/ceph/ceph/pull/48861 more elegant.

Signed-off-by: Zac Dover <zac.dover@gmail.com>
(cherry picked from commit 24ec058839a897270838473d1bc14c2eb19ee24e)

diff --git a/doc/rados/operations/cache-tiering.rst b/doc/rados/operations/cache-tiering.rst
index 00a3f37f93715b9775158c3bcafd158895792184..a9e7984d45dc67a13ed7448d094db51d4136d511 100644 (file)
--- a/doc/rados/operations/cache-tiering.rst
+++ b/doc/rados/operations/cache-tiering.rst
@@ -45,18 +45,22 @@ and the backing storage tier automatically. However, admins have the ability to
 configure how this migration takes place by setting the ``cache-mode``. There are
 two main scenarios:
 
-- **writeback** mode: When admins configure tiers with ``writeback`` mode, Ceph
-  clients write data to the base tier and receive an ACK from it. Then the cache
-  tiering agent compares ``osd_tier_default_cache_min_write_recency_for_promote``,
-  that means if the data is written over given times at a interval, it will
-  be promoted to the cache tier. When Ceph clients need data that resides in
-  the base tier, the cache tier will proxy read the data from the base tier
-  and return to the client. Meanwhile, as same as write does, the cache tiering
-  agent will decide whether migrating the data to the cache tier based on
-  ``osd_tier_default_cache_min_read_recency_for_promote``. After the data
-  is promoted to from the base tier, the Ceph client can perform I/O using
-  the cache tier, until the data becomes inactive. This is ideal for mutable
-  data (e.g., photo/video editing, transactional data, etc.).
+- **writeback** mode: If the base tier and the cache tier are configured in
+  ``writeback`` mode, Ceph clients receive an ACK from the base tier every time
+  they write data to it. Then the cache tiering agent determines whether
+  ``osd_tier_default_cache_min_write_recency_for_promote`` has been set. If it
+  has been set and the data has been written more than a specified number of
+  times per interval, the data is promoted to the cache tier.
+
+  When Ceph clients need access to data stored in the base tier, the cache
+  tiering agent reads the data from the base tier and returns it to the client.
+  While data is being read from the base tier, the cache tiering agent consults
+  the value of ``osd_tier_default_cache_min_read_recency_for_promote`` and
+  decides whether to promote that data from the base tier to the cache tier.
+  When data has been promoted from the base tier to the cache tier, the Ceph
+  client is able to perform I/O operations on it using the cache tier. This is
+  well-suited for mutable data (for example, photo/video editing, transactional
+  data).
 
 - **readproxy** mode: This mode will use any objects that already
   exist in the cache tier, but if an object is not present in the