2.11 Configure disk offload
If the estimated total size of all cached objects is bigger than the available memory, you can enable the disk offload option in WebSphere Application Server. We would expect most WebSphere Commerce sites to use disk offload, unless a Web site has a small catalog.
Priority weighting is used in conjunction with the least recently used (LRU) algorithm to move objects from the cache onto disk. You configure priorities for the cached objects in the cachespec.xml file. A higher priority entry is less likely to be moved to disk.
If you decide to use the disk offload option, also configure your file system for fast I/O access. Depending on your hardware and software, you can use various disk striping or caching techniques. Disk offload is configured on the same panel where you enable the DynaCache service. You should investigate using a high-speed Storage Area Network with memory.
The three settings related to the disk offload configuration are the following:
| Enable disk offload: Specifies whether disk offload is enabled. If a cache entry that was moved to disk is needed again, it is moved back to memory from the file system. |
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| Offload location: Specifies the location on the disk to save cache entries when disk offload is enabled. If disk offload location is not specified, the default location is used: |
$install_root/temp/node/servername/_DynaCache/cacheJNDIname
If a disk offload location is specified, the node, server name, and cache instance name are appended.
For example, $install_root/diskoffload generates the location as $install_root/diskoffload/node/servername/cacheJNDIname. This value is ignored if disk offload is not enabled.
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| Flush to disk: Specifies if in-memory cached objects are saved to disk when the server is stopped. This value is ignored if Enable disk offload is not selected. |