[Cassandra Wiki] Update of "FAQ" by tuxracer69

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The "FAQ" page has been changed by tuxracer69.
The comment on this change is: SSTables and Memtables.
http://wiki.apache.org/cassandra/FAQ?action=diff&rev1=23&rev2=24

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   * [[#modify_cf_config|Can I add/remove/rename Column Families on a working cluster?]]
   * [[#node_clients_connect_to|Does it matter which node a Thrift client connects to?]]
   * [[#what_kind_of_hardware_should_i_use|What kind of hardware should I run Cassandra on?]]
+  * [[#architecture|What are SSTables and Memtables?]]
  
  <<Anchor(cant_listen_on_ip_any)>>
  == Why can't I make Cassandra listen on 0.0.0.0 (all my addresses)? ==
@@ -74, +75 @@

  
  So to summarize, use a different device for your `CommitLogDirectory`; it needn't be large, but it should be fast enough to receive all of your writes. Then, use one or more devices for `DataFileDirectories` and make sure they are both large enough to house all of your data, and fast enough to satisfy your reads and to keep up with flushing and compaction.
  
+ <<Anchor(architecture)>>
+ ==What are SSTables and Memtables?==
+ A Memtable is Cassandra's in-memory representation of key/value pairs
+ before the data gets flushed to disk as an SSTable.  An SSTable
+ (terminology borrowed from Google) stands for Sorted Strings Table and
+ is a file of key/value string pairs, sorted by keys.
+