Nick Piggin wrote: > OK right. As far as I can see, the algorithm in the RAID1 code > is used to select the best drive to read from? If that is the > case then I don't think it could make better decisions given > more knowledge. How about if it just asks the elevator whether or not a given read is a good fit with its current workload? I saw in 2.5 where the balance code is looking at the number of pending requests and if it's zero then it sends it to that device. Somehow I think something better than that could be done, anyway. > It seems to me that a better way to layer it would be to have > the complex (ie deadline/AS/CFQ/etc) scheduler handling all > requests into the raid block device, then having a raid > scheduler distributing to the disks, and having the disks > run no scheduler (fifo). That only works if RAID1 is working at the physical disk level (which it should be AFAIC but people want flexibility to mirror partitions.) > In practice the current scheme probably works OK, though I > wouldn't know due to lack of resources here :P I've been playing with the 2.4 read balance code and have some improvements, but real gains need a new approach. (cc'd to linux-raid) -- Chuck - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
