[DRBD-user] drbd performance with GbE in connected mode

Ralf Gross Ralf-Lists at ralfgross.de
Mon Jan 15 22:46:10 CET 2007


Ross S. W. Walker schrieb:
> > It seems that 
> > 
> > a. changing the net parameters did help 
> > 
> >  sndbuf-size       240k;
> >  max-buffers      20480;
> >  max-epoch-size   16384;
> >  unplug-watermark 20480;
> > 
> > b. changing the bonding mode of the interfaces from balance-rr to
> >    balance-xor did help too.
> > 
> > I now get about 85MB/s. Maybe that's by accident, but I could watch
> > the write performance go down when increasing the sndbuf-size.
> 
> Well I can see increasing sndbuf as increasing latency, so it makes
> sense that decreasing it would also decrease latency a bit, why not try
> 128K and see where that puts you. If you have direct connections and a
> fast network, there is no real need to have a large sndbuf. If I was
> using Prot A and a slow network of T1s then I would use a very large
> sndbuf.
> 
> Statistically speaking though when doing a benchmark over a short period
> of time 82-83-85 MB/s are about the same. I find that a 15 minute run
> will normally get rid of the 3-5 MB/s swings between runs and narrow it
> down to 1-2 MB/s swings.
> 
> It looks like you are approaching the part of tuning were you are
> receiving diminishing returns and will need to do more and more tuning
> to squeeze less and less out, so I would say that 85 MB/s is what your
> gonna see unless you can find a way to run drbd with multiple paths,
> which I don't think it has the capability to do.
> 
> Well let me know if you can squeeze any more out of it. You might want
> to see if there is any filesystem optimizations you can do now to get
> some extra performance out of it.

Ok, now I changed the fs of the 300GB lvm lv to xfs.

Sequential Writes
File  Blk   Num                   Avg    Maximum    Lat%    Lat%    CPU
Size  Size  Thr   Rate  (CPU%)  Latency  Latency    >2s     >10s    Eff
---- ----- ---  ------ ------ --------- ---------- -------- ------- ----
8000  4096    1   92.29 40.35%   0.152   1435.65   0.00000  0.00000  229

Random Writes
File  Blk   Num                   Avg    Maximum    Lat%     Lat%    CPU
Size  Size  Thr   Rate  (CPU%)  Latency  Latency    >2s      >10s    Eff
----- ----- ---  ------ ------ -------- ---------  -------- -------- ----
8000  4096    1   22.11 23.88%   0.031     0.13    0.00000  0.00000   93


I did some tests at the end of last year and xfs seemed to be faster than ext3.
But I didn't expect that this would impact the performance of drbd in connected
mode that much. Especially the random writes are much higher than with ext3.

I've to think about that...

ralf



More information about the drbd-user mailing list