Kishore Jalleda wrote:
Hi All,
We have a production Database, running mysql 4.0.17 , on a
Poweredge 2650 with 3 GB RAM, and dual Xeon 2.4 GHZ, the server
averages between 100 and 200 qps ( ,also and the CPU/MEM load is
pretty low and is extremely fast except for once in a while may be 1
in 1 queries take mote than 3 seconds to execute
(slow_query_time), and the status of the query is always writing to
net
Initially the NIC was an Intel 10/100, then the slow queries were a
lot more, then I started using the Broadcom Gigabit port that comes
with the 2650, and recently I also started load balancing the traffic
between the two Broadcomm NIC'S using the Basp Module, so that I
effectively have a 200 MBPS full duplex link( the switch connected has
only FE ports), with this setting the slow queries have decreased a
lot, but they do come up once in a while..
There is no lock time in any of them, I have tried using both InnoDB
and MyISAM, but they dont seem to go away, so I was wondering why
there are still few queries which still have writing to Net in the
status line and sometimes take 30-50 seconds to execute, note that if
the queries are run in any mysql client they run in less than 0.005
seconds, so I am pretty sure its the network thats the bottleneck, and
buying a Gigabit capable switch is not an option now, also sometimes
the traffic on the server goes upto 35MBPS.
So why is mysql not sending the results back to the client and
sometimes waiting soo long, also while mysql is waiting for a long
query( in the Writing to Net status) hundreds of other queries are
executed extrelmely fast.
I am not very familiar with how mysql handles network packets, and why
its holding back ...
If the network is a bottleneck, certainly this could result in
long Writing to Net status. One could imagine network congestion
causing repeated TCP/IP retries, etc. It might just be that your
server is heavily loaded and certain threads are not getting enough
resources to finish processing.
Things like this are usually far to complex to diagnose simply,
and if you want expert help, I would recommend you engage with
our professional services team with either of these packaged
consulting solutions:
http://www.mysql.com/consulting/packaged/performance.html
http://www.mysql.com/consulting/packaged/rapidresponse.html
Regards,
Josh
--
Josh Chamas
Director, Professional Services
MySQL Inc., www.mysql.com
Get More with MySQL! www.mysql.com/consulting
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