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What cache hits and misses are

Cache hits and misses indicate if the data requested by the client is served directly from the FlexCache volume or from the origin volume. The occurrence of a cache hit or miss depends on factors such as availability of the requested data in the cache, the attribute cache timeout values, and the difference between attributes of a file in the cache and the origin.

Cache hits

When a client sends a read request, if the relevant block is cached in the FlexCache volume, the data is read directly from the FlexCache volume. This is called a cache hit. Cache hits are the result of a previous request.

A cache hit can be one of the following types:
  • Hit: The requested data is already cached and the FlexCache volume serves the read request without accessing the origin volume.
  • Hit-Verify: The requested data is already cached but the FlexCache volume needs to verify the attributes of the cached file with those on the origin. The FlexCache does not request any data from the origin volume while performing this verification process.

Cache misses

If the requested data is not on the FlexCache volume, or if the data has changed since it was cached, the caching system loads the data from the origin volume, and then returns it to the requesting client. This is called a cache miss.

A cache miss can be one of the following types:
  • Miss: The requested data is not cached and is read from the origin volume.
  • Miss-Verify: The requested data is cached but the file attributes have changed since it was last cached. Therefore, the file is removed from the cache, and the requested data is read from the origin.