[OpenAFS-devel] Re: Backups using commercial products

[Sam Hartman]

>>>>> "Lyle" == Lyle Seaman <lws@spinnakernet.com> writes:

    >> So, does RX allow a procedure to write bytes into the queue
    >> past the point where the window is full?  I.E. does it have a
    >> concept similar to tcp|udp sendspace?  Shouldn't that smooth
    >> out some of the disk seek delays?

    Lyle> No it doesn't have any such thing, nor an equivalent to
    Lyle> sendfile().  Those sorts of things would help, but why
    Lyle> reinvent them?  

Because fixing RX may be easier than doing something else?
OTOH, BEEP exports approximately the right interface to replace the RX stream layer.


    Lyle> And they wouldn't help much with the disk
    Lyle> seek delays. The only way to minimize the effect of the disk
    Lyle> seeks is to batch up more I/O at one time.

Can you give evidence to support this?  It seems that even if the
seeks are slow, if you always have data ready to send immediately when
the client sends you an ack, then you may use significantly more CPU
than you need because of overhead, but you will still utilize network
effectively.

It seems that you could do a lot by using async IO and by adding such
a facility to RX to continue to do work past the window.