vmstat does not have an option to log timestamps which may cause its logs to be difficult to interpret later.
The workaround is to use awk to generate timestamp and print vmstat output plus data:
# vmstat 1 | awk '{now=strftime("%Y-%m-%d %T "); print now $0}'
2013-06-26 21:47:41 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
2013-06-26 21:47:41 r b swpd free buff cache si so bi bo in cs us sy id wa st
2013-06-26 21:47:41 1 0 0 385944 71768 517152 0 0 96 28 1018 118 3 5 89 3 0
2013-06-26 21:47:42 0 0 0 385944 71768 517152 0 0 0 0 1008 65 0 1 99 0 0
2013-06-26 21:47:43 0 0 0 385944 71768 517152 0 0 0 0 1023 73 0 0 100 0 0
Fortunately iostat on Linux have -t switch which adds timestamp for every output.
However if you're using iostat on system where -t switch is not available you may use the same trick we did with vmstat.
Default settings for NICs is good for most cases however there are times when you need to do some performance tuning.
When you start to observe increasing drops of RX packets it means that your system cannot process incoming packets fast enough. You can verify on your monitoring system to correlate this issue with increased network traffic at the same time.
# ifconfig
eth0 Link encap:Ethernet HWaddr 00:22:19:50:ea:76
inet addr:192.168.x.x Bcast:192.168.x.x Mask:255.255.xxx.xxx
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3208932 errors:0 dropped:19188 overruns:0 frame:0
TX packets:1543138 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
First verify current NIC settings:
# ethtool -g eth0
Ring parameters for eth0:
Pre-set maximums:
RX: 1020
RX Mini: 0
RX Jumbo: 4080
TX: 255
Current hardware settings:
RX: 255
RX Mini: 0
RX Jumbo: 0
TX: 255
Increasing ring buffer for rx should fix this issue:
# ethtool -G eth0 rx 512
To have this settings persistent make sure you add this command to /etc/rc.local script.
