DEV: doc changes per RED-137284 (#746)

* DEV: doc changes per RED-137284

* Some fine tuning

* Apply review comments

* Apply more review feedback

Author: dwdougherty

content/commands/info/index.md

@@ -515,3 +515,24 @@ It won't be included when `INFO` or `INFO ALL` are called, and it is returned on
 **A note about the word slave used in this man page**: Starting with Redis 5, if not for backward compatibility, the Redis project no longer uses the word slave. Unfortunately in this command the word slave is part of the protocol, so we'll be able to remove such occurrences only when this API will be naturally deprecated.
 
 **Modules generated sections**: Starting with Redis 6, modules can inject their information into the `INFO` command. These are excluded by default even when the `all` argument is provided (it will include a list of loaded modules but not their generated info fields). To get these you must use either the `modules` argument or `everything`.
+
+## Redis Software and Redis Cloud compatibility
+
+| Redis<br />Enterprise | Redis<br />Cloud | <span style="min-width: 9em; display: table-cell">Notes</span> |
+|:----------------------|:-----------------|:------|
+| <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> | <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> | In Redis Enterprise, `INFO` returns a different set of fields than Redis Community Edition.<br />Not supported for [scripts]({{<relref "/develop/interact/programmability">}}). |
+
+Note: key memory usage is different on Redis Software or Redis Cloud active-active databases than on non-active-active databases. This is because memory usage includes some amount of CRDB overhead.
+
+Additionally, for JSON keys, Redis implements a “shared string” mechanism to save memory when the same JSON field names or field values of type string are used more than once (either inter-key or intra-key).
+In such cases, instead of storing the field names or values many times, Redis stores them only once. This mechanism is not in place for active-active databases.
+
+On non-active-active databases, `INFO` (Memory > used_memory) reports that the shared memory is counted, but only once for all keys. On active-active databases, there is no shared memory, so if strings are repeated, they are stored multiple times.
+
+**Example**
+
+Suppose you have ten JSON keys, and each key has 5KB of unique content and 5KB of shared content.
+
+For non-active-active databases, `INFO` (used_memory) would report (10 keys * 5KB) + 5KB ~= 55KB. The last term, "+ 5KB", is the size of the shared content.
+
+For active-active databases, `INFO` (used_memory) would report 10 keys * 20KB ~= 200KB. This number includes some amount of CRDB overhead per JSON key.

content/commands/memory-usage/index.md

@@ -87,3 +87,11 @@ OK
 > MEMORY USAGE foo3
 (integer) 160
 ```
+
+## Redis Software and Redis Cloud compatibility
+
+| Redis<br />Enterprise | Redis<br />Cloud | <span style="min-width: 9em; display: table-cell">Notes</span> |
+|:----------------------|:-----------------|:------|
+|<span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> | <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> | Not supported for [scripts]({{<relref "/develop/interact/programmability">}}) in Redis versions earlier than 7. |
+
+Note: key memory usage is different on Redis Software or Redis Cloud active-active databases than on non-active-active databases. This is because memory usage includes some amount of CRDB overhead.