This is a patch against Linux kernel 2.6.13 to add another path selecting method to device-mapper: the load-balance selector. This new selector will keep track of the number of request sent to each path which have not yet completed. When selecting a new path it will choose the one with the least amount of outstanding requests. In case the number of requests is the same for all paths the behaviour is the same as for the round-robin selector (each path would be used in turn). The benefits of this approach is that it will evenly spread I/O to all paths and should adapt to paths that are faster or slower. The load-balance selector accepts one argument which has the same meaning as for the round-robin selector (the number of requests that are sent to the same path before selection is done). The status device-mapper call will additionally show the number of requests that are pending. I tried to keep the changes to common code as small as possible. The current solution requires only one additional function hook which is called whenever a request is successfully mapped. Comments are welcome. Regards, Stefan Bader SW Linux on zSeries Development & Services Stefan.Bader@xxxxxxxxxx ---------------------------------------------------------------------------------- When all other means of communication fail, try words.
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dm-load-balance.patch
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