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Re: [dm-devel] [RFC][PATCH] dm-cache: block level disk cache target for device mapper



On 11/30/06, Jens Wilke <jens wilke de ibm com> wrote:
- You don't keep track of I/O on the fly to the cache that is mapped
directly in cache_hit(). How do you make sure that this I/O is completed
before you replace a cache block?

The previous I/O from cache hit and the later I/O for cache
replacement should be queued in order on the cache block device - is
this a safe assumption?

- The cache block index is hashed, this means the cache data blocks are not
clustered. I don't think you can solve this problem with a proper hash function.
Perhaps you should consider a (B-)Tree structure for that.

The current hash algorithm does clustering to some extent by mapping
consecutive blocks from the source device to consecutive blocks on the
cache device. But I agree that more sophisticated algorithms can be
studied.

Thanks a lot for the suggestions. I will try to incorporate them in
the next patch.

- Ming


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