InnoDB memcached Architecture daemon_memcached_w_batch_size  configuration options. Batch size options default to a value of 1 for maximum reliability. You may already be familiar with using  memcached  with MySQL, as described in Using MySQL with memcached . This section describes how features of the integrated  InnoDB memcached  plugin differ from traditional  memcached . For comparison with traditional  memcached , see Installing  memcached . For comparison with traditional  memcached , see  memcached  Deployment. For comparison with traditional  memcached , see Data Expiry. 3355 •Namespaces:  memcached  is like a large directory where you give files elaborate names with prefixes and suffixes to keep the files from conflicting. The  daemon_memcached  plugin lets you use similar naming conventions for keys, with one addition. Key names in the format •Expiry: By default (that is, using the  innodb_only  caching policy), the latest data from the  InnoDB table is always returned, so the expiry options have no practical effect. If you change the caching policy to  caching  or  cache_only , the expiry options work as usual, but requested data might be stale if it is updated in the underlying table before it expires from the memory cache. •Deployment: With traditional  memcached , it is typical to run large numbers of low-capacity  memcached servers. A typical deployment of the  daemon_memcached  plugin, however, involves a smaller number of moderate or high-powered servers that are already running MySQL. The benefit of this configuration is in improving efficiency of individual database servers rather than exploiting unused memory or distributing lookups across large numbers of servers. In the default configuration, very little memory is used for memcached , and in-memory lookups are served from the  InnoDB  buffer pool, which automatically caches the most recently and frequently used data. As with a traditional MySQL server instance, keep the value of the  innodb_buffer_pool_size  configuration option as high as practical (without causing paging at the OS level), so that as much work as possible is performed in memory. •Installation: The  memcached  library comes with the MySQL server, making installation and setup relatively easy. Installation involves running the  innodb_memcached_config.sql  script to create a  demo_test  table for  memcached  to use, issuing an  INSTALL PLUGIN  statement to enable the daemon_memcached  plugin, and adding desired  memcached  options to a MySQL configuration file or startup script. You might still install the traditional  memcached  distribution for additional utilities such as memcp ,  memcat , and  memcapable . •The ability to specify  memcached  options through the  daemon_memcached_option  configuration parameter. For example, you can change the port that  memcached  listens on, reduce the maximum number of simultaneous connections, change the maximum memory size for a key-value pair, or enable debugging messages for the error log. •The  innodb_api_trx_level  configuration option controls the transaction isolation level on queries processed by  memcached . Although  memcached  has no concept of transactions, you can use this option to control how soon  memcached  sees changes caused by SQL statements issued on the table used by the  daemon_memcached  plugin. By default,  innodb_api_trx_level  is set to  READ UNCOMMITTED . •The  innodb_api_enable_mdl  option can be used to lock the table at the MySQL level, so that the mapped table cannot be dropped or altered by DDL through the SQL interface. Without the lock, the table can be dropped from the MySQL layer, but kept in  InnoDB  storage until  memcached  or some other user stops using it. “MDL”  stands for “metadata locking” . Differences Between InnoDB memcached and Traditional memcached