2. Configure cache storage

The tasks for configuring cache storage depend on whether you use a memory cache or a disk cache.

To use a memory cache, customize the Cache Memory setting so that it includes enough memory to hold the contents of a cache. See Set cache memory for recommended cache memory sizes.

To use a disk cache, you must do the following:

  1. Prepare a storage device to hold the cache.

    The cache requires a specially formatted device. Devoting an entire device or disk partition to the cache is recommended. The minimum size for a cache is 16392 KB.

    To format the cache device:

    1. Choose a device to hold the cache. Ensure that no other program is using that storage space and that the device can be accessed as a raw (or character-formatted) device.
    2. Format the device by using the htcformat command. The syntax is as follows:
      htcformat raw_device_path [-blocksize block_size]
           [-blocks number_of_blocks]
      The -blocksize and -blocks arguments are optional. The default block size is 8192 bytes. If the number of blocks is not specified, the disk partition will be filled with as many blocks as it can contain.

      When specifying the device path, be sure to specify the raw device path.

      • On AIX platforms, the raw device path for a logical volume defined as /dev/lv02 is /dev/rlv02
      • On Linux platforms, you must first run the raw command prior to running htcformat to associate the raw device path with the real SCSI drive sdb1.
        raw /dev/raw/raw1 dev/sdb1
      • On HP-UX and Solaris platforms, the raw device path for a partition defined as /dev/dsk/c0t0d0s0 is /dev/rdsk/c0t0d0s0
      • On Windows platforms, the raw device path for a device defined as e: is \\.\e:

      See the reference material for your file system for additional information about accessing raw devices.

  2. Specify the cache device by using the CacheDev directive or the Cache Settings configuration form. You can specify more than one device.
CAUTION:
On Windows systems, the htcformat command does not automatically mark the cache device as unwritable.

If the operating system attempts to write to the cache device, cached data can be lost. To avoid this, you can use the Windows Disk Manager utility to prepare the disk before using the htcformat command. To prepare the disk, use the disk utility to delete the device or partition you want to use, then recreate it without formatting it. This causes the system to consider the device unavailable for system storage.