On 05/28/2015 05:05 PM, Ben RUBSON wrote:
So,
I played during hours with the dynamic resync rate controller.
Here are my settings :
c-plan-ahead 10; //10ms between my 2 nodes, but minimum 1 second
recommended here :
https://blogs.linbit.com/p/128/drbd-sync-rate-controller/
"c-plan-ahead 10" equals 1 second (the unit is tenth of seconds).
You can try to decrease that value further, because it makes the resync
rate controller
somewhat more aggressive, and that may effectively increase the resync
rate somewhat.
However, there is no guarantee that this will improve your resync rate
significantly,
because that is a side effect rather than a feature.
Well, I'm a little bit lost, I can't achieve to get resync with a
minimum rate of 400M when there are application IOs...
Here, Lars says :
http://lists.linbit.com/pipermail/drbd-user/2011-August/016739.html
The dynamic resync rate controller basically tries to use as much as
c-max-rate bandwidth, but will automatically throttle, if
- application IO on the device is detected (READ or WRITE), AND the
estimated current resync speed is above c-min-rate
- the amount of in-flight resync requests exceeds c-fill-target
However, does DRBD throttle application IOs when resync rate is lower
than c-min-rate ?
No, it does NOT throttle application IO.
What c-min-rate does, is:
IF the backend device has significantly more
traffic going on than can be accounted for by
the traffic caused by the resync itself,
AND the current resync rate is greater than
c-min-rate, the resync will be throttled
in order to prioritize application IO over
resync IO.
However, if the resync rate is already less than
c-min-rate, then this feature does NOT throttle
application IO to prioritize resync IO over
application IO
(actually, in the case that the resync rate is
less than c-min-rate, this feature does nothing)
best regards,
Robert
[Sent again, I forgot to reply to the mailing list too]
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