doc: Added latency comment.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Fixing index references.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added cluster map and CRUSH definitions.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added glossary references and index references.

fixes: #3321

Signed-off-by: John Wilkins <john.wilkins@inktank.com>
doc: Added index reference.

Signed-off-by: John Wilkins <john.wilkins@inktank.com>