[DRBD-user] The effects of duplex mismatch on a cluster running drbd

Maurice Volaski mvolaski at aecom.yu.edu
Fri Jul 15 08:44:14 CEST 2005

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

I have running a pair of servers using drbd to do mirroring. Primary 
is using dual bonded gigabit. Secondary didn't have gigabit yet. And 
the 100 Mbit it was running was incorrectly set to half duplex.

Hearbeat dropped packets. That seems expected.
Drbd was continually dropping the connection. That seems expected.
But here's something interesting: it affected services on the 
primary. Both netatalk and smb clients were dropping connections 
frequently. I'm assuming this is due to the way protocol C works. IO 
isn't flagged as done until the secondary acknowledges it. And a 
duplex mismatch majorly impacts network operation.

This is in effect means that anything that impacts IO on the 
secondary impacts the primary's functionality. They're like siamese 
computers :-)

Maurice Volaski, mvolaski at aecom.yu.edu
Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva University

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