Using 2 partitions as cache_dir...

Hi,

    I am wonder that how to use 2 partitions for cache storage?
    The explanation in configuration file doesn't say clearly.
    What should I set for the cache size ? I have 2x2G HD, for example:

    /cache1 & /cache2

    so, I use:

    cache_dir /cache1
    cache_dir /cache2

        and

    cache_swap 4000

    is it right? Will it possible that when /cache1 is full and /cache2
    is still in low level usage ?

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Alex Lau