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# ssd_cache dictionary layout types

> Store dictionary data on SSD with an in-memory index: ssd_cache or complex_key_ssd_cache types

<h2 id="ssd_cache">
  ssd\_cache
</h2>

Similar to `cache`, but stores data on SSD and index in RAM. All cache dictionary settings related to update queue can also be applied to SSD cache dictionaries.

The dictionary key has the [UInt64](/reference/data-types/int-uint) type.

<Tabs>
  <Tab title="DDL">
    ```sql theme={null}
    LAYOUT(SSD_CACHE(BLOCK_SIZE 4096 FILE_SIZE 16777216 READ_BUFFER_SIZE 1048576
        PATH '/var/lib/clickhouse/user_files/test_dict'))
    ```
  </Tab>

  <Tab title="Configuration file">
    ```xml theme={null}
    <layout>
        <ssd_cache>
            <!-- Size of elementary read block in bytes. Recommended to be equal to SSD's page size. -->
            <block_size>4096</block_size>
            <!-- Max cache file size in bytes. -->
            <file_size>16777216</file_size>
            <!-- Size of RAM buffer in bytes for reading elements from SSD. -->
            <read_buffer_size>131072</read_buffer_size>
            <!-- Size of RAM buffer in bytes for aggregating elements before flushing to SSD. -->
            <write_buffer_size>1048576</write_buffer_size>
            <!-- Path where cache file will be stored. -->
            <path>/var/lib/clickhouse/user_files/test_dict</path>
        </ssd_cache>
    </layout>
    ```
  </Tab>
</Tabs>

<br />

<h2 id="complex_key_ssd_cache">
  complex\_key\_ssd\_cache
</h2>

This type of storage is for use with composite [keys](/reference/statements/create/dictionary/attributes#composite-key). Similar to `ssd_cache`.