[linux-lvm] pvmove speed

L A Walsh lvm at tlinx.org
Fri Feb 17 23:00:25 UTC 2017

Roy Sigurd Karlsbakk wrote:
> I get 200MB on a cold day and 500 on a nice one from this SAN. These 40-50MB/s seem really being limited by pvmove alone. Nothing else shows this limit. That's why I'm asking.
    200-500... impressive for a SAN... but considering the bandwidth
you have to the box (4x1+10), I'd hope for at least 200 (what I get
w/just a 10)... so must be some parallel TCP channels there... he..
What showed those speeds?  I'm _guessing_, but its likely that pvmove
is single threaded.  So could be related to the I/O transfer size as
@pattonme was touching on, since multi-threaded I/O can slow things
down for local I/O when local I/O is in the .5-1GBps and higher range.

    Curious -- do you know your network's cards' MTU size?
I know that even w/1Gb cards I got 2-4X speed improvement over
standard 1500 packets (run 9000/9014 byte MTU's over local net).

    I'd have to look at the source for more info...


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