doc: Fix cache tier docs

The instructions for 'osd tier add' were plain
wrong, claiming that the cache mode could
be passed as a third argument.

Signed-off-by: John Spray <john.spray@inktank.com>

diff --git a/doc/rados/operations/cache-tiering.rst b/doc/rados/operations/cache-tiering.rst
index e733c7e29a4e17ec97358fc08b931a07f06589b0..dcefdf2ff585bbc2abd67221100a71ad1ac0f397 100644 (file)
--- a/doc/rados/operations/cache-tiering.rst
+++ b/doc/rados/operations/cache-tiering.rst
@@ -112,24 +112,23 @@ have the high performance drives while omitting the hosts that don't. See
 `Placing Different Pools on Different OSDs`_ for details.
 
 
-In subsequent examples, we will refer to the cache pool as ``hot-storage``.
+In subsequent examples, we will refer to the cache pool as ``hot-storage`` and
+the backing pool as ``cold-storage``.
 
 
 Creating a Cache Tier
 =====================
 
-Setting up a cache tier involves naming a backing storage pool, 
-a cache pool and the cache mode. ::
+Setting up a cache tier involves associating a backing storage pool with
+a cache pool ::
 
-       ceph osd tier add {storagepool} {cachepool} [writeback|readonly]
+       ceph osd tier add {storagepool} {cachepool}
 
-To set up a writeback (read/write) cache pool ``hot-storage`` for pool 
-``cold-storage``, execute the following::
+For example ::
 
-       ceph osd tier add cold-storage hot-storage [cache-mode]
+       ceph osd tier add cold-storage hot-storage
 
-You can specify the cache mode when creating a tier. To set the cache mode
-in a subsequent step, execute the following:: 
+To set the cache mode, execute the following::
 
        ceph osd tier cache-mode {cachepool} {cache-mode}
 
@@ -360,4 +359,4 @@ disable and remove it.
 .. _Pools - Set Pool Values: ../pools#set-pool-values
 .. _Placing Different Pools on Different OSDs: ../crush-map/#placing-different-pools-on-different-osds
 .. _Bloom Filter: http://en.wikipedia.org/wiki/Bloom_filter
-.. _CRUSH Maps: ../crush-map
\ No newline at end of file
+.. _CRUSH Maps: ../crush-map