Foolcache behaves like other block caches like flashcache, dm-cache or bcache. The unique feature that foolcache provides is that, data stored in cache media is organized exactly the same as in origin, so foolcache can be used in conjunction with a background replicator.
Foolcache has the following features:
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Copy-on-Read(CoR), which copies data when a block it is read.
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The ability to transform a cache into a full replica, without data movement.
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Full-sized cache media, which eliminates the need for cache invalidation. "full" and "fool" are homophonic.
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In the future, Copy-on-Write(CoW), which copies data when a block is partially written.
Foolcache judges whether a block has been cached or not by looking-up a bitmap, and foolcache stores meta-data at the tail of the cache media.