new class / geom_cache / request for comments

[Mike Jakubik]

R. B. Riddick wrote:
> Yes, I think so...
> But geom_cache is just useful, when file system's buffer cache cannot help.
>
> E. g.:
> A degraded RAID5 on 4 consumers (3 good plus 1 failed).
> When we want to get a data block, that resides on the failed consumer, we have
> to read all corresponding blocks (2+1) in order to rebuild the missing block.
> When we do a sequential read, we would have to read the consumers, that hold
> the data blocks twice (2 x 2).
> So the geom_cache could help here (2+1 real reads plus 2 from the cache), if
> the provider is not too busy.
>   

Wouldn't it make more sense to modify geom_raid5 to include this 
behavior, instead of writing a new and separate geom class that has only 
one useful function?