docs/rados/operations/stretch-mode: warn device class is not supported

Signed-off-by: Kamoltat Sirivadhna <ksirivad@redhat.com>
(cherry picked from commit aa1d8cf4fa321e24e850bd5f687a6ddad3ce05e3)

diff --git a/doc/rados/operations/stretch-mode.rst b/doc/rados/operations/stretch-mode.rst
index a752bf54118703115d1ec5edd848de5b523a5148..37c1de14b838c442305299aa6309a5430e3c2a10 100644 (file)
--- a/doc/rados/operations/stretch-mode.rst
+++ b/doc/rados/operations/stretch-mode.rst
@@ -260,8 +260,21 @@ SSDs (including NVMe OSDs). Hybrid HDD+SDD or HDD-only OSDs are not recommended
 due to the long time it takes for them to recover after connectivity between
 data centers has been restored. This reduces the potential for data loss.
 
-In the future, stretch mode might support erasure-coded pools and might support
-deployments that have more than two data centers.
+.. warning:: Device class is currently not supported in stretch mode.
+   For example, the following rule containing ``device class`` will not work::
+
+      rule stretch_replicated_rule {
+                 id 2
+                 type replicated class hdd
+                 step take default
+                 step choose firstn 0 type datacenter
+                 step chooseleaf firstn 2 type host
+                 step emit
+      }
+
+In the future, stretch mode could support erasure-coded pools,
+enable deployments across multiple data centers,
+and accommodate various device classes.
 
 Other commands
 ==============