Re: IOCache vs. block cache

On Thu, Jun 17, 2010 at 8:51 AM, Ingo Weinhold <[email protected]> wrote:
> I think eventually the block cache should be rewritten to be VMCache based
> with on-demand mapping of hot blocks, but for the time being a simpler
> solution would be possible: The IOCache could be extended to make it
> possible to lay it under the IOSchedulerSimple. This would give us a
> VMCache based cache close to the device. The block cache could then work
> with a very small, limited (!) set of unused blocks.

A question - what cases would the block cache actually used in? It
seems as if the file / IO caches cover the cases of actual file data,
which would seem to only leave things like FS metadata blocks going
directly through the block cache.  And even that seems somewhat
redundant if the IOCache is also at the device level. Am I missing
something?

Regards,

Rene

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