[DRBD-user] drbd, blocked processes in D state, send-Q, recv-Q

Roland Friedwagner roland.friedwagner at wu.ac.at
Mon Aug 25 14:36:33 CEST 2014

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


blocking is a normal behavor when you replication link TCP queues 
becomes full.

You may increase the linux kernel defaults like this in /etc/sysctl.conf
  net.core.rmem_default = 16777216
  net.core.wmem_default = 16777216
  net.core.rmem_max = 33554432
  net.core.wmem_max = 33554432
  net.ipv4.tcp_rmem = 131072 16777216 33554432
  net.ipv4.tcp_wmem = 131072 16777216 33554432
  net.ipv4.tcp_mem  = 131072 16777216 33554432
and switch to protocol A.
But after about 16MB unwritten data send to secondary it will block.

If you switch to drbd 8.4 is is pssible to switch automaticaly to resync
with a on-congestion policy.

Regards roland

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