Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 15 Apr 2003 14:33:51 -0400 | From | Chuck Ebbert <> | Subject | Re: Benefits from computing physical IDE disk geometry? |
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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)
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