Support for a persistent or 'warm' VxVM cache

A warm cache means that the contents of the cache remain persistent across planned reboots. By default, SmartIO does not provide a warm cache capability for VxVM caches. The cache area metadata is not flushed during a system shut down. The cache is invalidated after the system reboot, and whenever the volumes need to be restarted. This behavior is known as a 'cold' cache.

Symantec does not recommend that you configure a warm cache, because it may lead to data inconsistency. However, in some circumstances, when proper care is taken, it can be beneficial to configure a warm cache. For example, in the case of a controlled, planned reboot you may want to explicitly enable a warm cache. This feature enables you to flush the metadata to the cache, thus creating a warm cache.

If you enable a persistent or warm cache, VxVM detects and invalidates the persistent cache if the data volume was updated while the cache was offline. In clustered environments, if the cache area on a node is persisted during a planned shutdown on that node, and the data volume is updated on another node, the warm cache contents are treated as stale and persisted cached data is evicted.

To enable a warm cache for a planned reboot

  1. Before the system reboot, shut down all the applications.
  2. Create the warm cache by running the following command:
    # sfcache offline --flushmeta cachearea_name

    If desired, you can add this command to your shutdown script.

    You must run the above command before the application restart or system reboot. If not, the data in the cache is purged and the cache is not populated after the reboot.