All links check out as full duplex gigabit with ifconfig and ethtool.
Ifconfig reports no dropped packets or retransmits. A tcpdump shows no
retransmits, but shows significantly smaller packets and fewer outstanding
packets between acks.
But iperf in UDP mode shows a consistent 1.5% lost
Hey Scott,
This is indeed really strange... if you do a straight hadoop fs -put with
dfs.replication set to 1 from one of the DNs, does it upload slow? That
would cut out the network from the equation.
-Todd
On Fri, Apr 16, 2010 at 5:29 PM, Scott Carey sc...@richrelevance.comwrote:
I have two
Ok, so here is a ... fun result.
I have dfs.replication.min set to 2, so I can't just do
hsdoop fs -Ddfs.replication=1 put someFile someFile
Since that will fail.
So here are two results that are fascinating:
$ time hadoop fs -Ddfs.replication=3 -put test.tar test.tar
real1m53.237s
user
More info -- this is not a Hadoop issue.
The network performance issue can be replicated with SSH only on the links
where Hadoop has a problem, and only in the direction with a problem.
HDFS is slow to transfer data in certain directions from certain machines.
So, for example, copying from
Checked link autonegotiation with ethtool? Sometimes gige will autoneg to
10mb half duplex if there's a bad cable, NIC, or switch port.
-Todd
On Fri, Apr 16, 2010 at 8:08 PM, Scott Carey sc...@richrelevance.comwrote:
More info -- this is not a Hadoop issue.
The network performance issue can
