[gpfsug-discuss] Steps for gracefully handling bandwidth reduction during network maintenance

[Skylar Thompson]

IIRC, maxMBpS isn't really a limit, but more of a hint for how GPFS should
use its in-memory buffers for read prefetches and dirty writes.

On Mon, Jun 17, 2019 at 09:31:38AM -0700, Alex Chekholko wrote:
> Hi Chris,
> 
> I think the next thing to double-check is when the maxMBpS change takes
> effect.  You may need to restart the nsds.  Otherwise I think your plan is
> sound.
> 
> Regards,
> Alex
> 
> 
> On Mon, Jun 17, 2019 at 9:24 AM Christopher Black <cblack at nygenome.org>
> wrote:
> 
> > Our network team sometimes needs to take down sections of our network for
> > maintenance. Our systems have dual paths thru pairs of switches, but often
> > the maintenance will take down one of the two paths leaving all our nsd
> > servers with half bandwidth.
> >
> > Some of our systems are transmitting at a higher rate than can be handled
> > by half network (2x40Gb hosts with tx of 50Gb+).
> >
> > What can we do to gracefully handle network maintenance reducing bandwidth
> > in half?
> >
> > Should we set maxMBpS for affected nodes to a lower value? (default on our
> > ess appears to be maxMBpS = 30000, would I reduce this to ~4000 for 32Gbps?)
> >
> > Any other ideas or comments?
> >
> > Our hope is that metadata operations are not affected much and users just
> > see jobs and processes read or write at a slower rate.
> >
> >
> >
> > Best,
> >
> > Chris
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-- 
-- Skylar Thompson (skylar2 at u.washington.edu)
-- Genome Sciences Department, System Administrator
-- Foege Building S046, (206)-685-7354
-- University of Washington School of Medicine