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.
If you had issues with I/O paths and they have been fixed you might want to reset error counters to keep a clean view.
There are two ways to achieve this:
- error counters will be automatically cleared during machine reboot
- by running powermt restore command
powermt restore will check I/O paths and update their current status, additionally it will clear Q-IOs and error counters.
# powermt display
Symmetrix logical device count=0
CLARiiON logical device count=1
Hitachi logical device count=0
Invista logical device count=0
HP xp logical device count=0
Ess logical device count=0
HP HSx logical device count=0
======================================================================
--- Host Bus Adapters --- ------ I/O Paths ----- ------ Stats ------
### HW Path Summary Total Dead IO/Sec Q-IOs Errors
======================================================================
1 qla2xxx optimal 2 0 - 0 77
2 qla2xxx optimal 2 0 - 0 0
# powermt restore
# powermt display
Symmetrix logical device count=0
CLARiiON logical device count=1
Hitachi logical device count=0
Invista logical device count=0
HP xp logical device count=0
Ess logical device count=0
HP HSx logical device count=0
======================================================================
--- Host Bus Adapters --- ------ I/O Paths ----- ------ Stats ------
### HW Path Summary Total Dead IO/Sec Q-IOs Errors
======================================================================
1 qla2xxx optimal 2 0 - 0 0
2 qla2xxx optimal 2 0 - 0 0
NIS SERVER SETUP:
1. Install required packages:
# yum install ypserv portmap
2. Edit /etc/sysconfig/network and add static NIS ports:
YPSERV_ARGS="-p 841"
YPPASSWDD_ARGS="-p 842"
YPXFRD_ARGS="-p 843"
To verify currently used ports run:
# rpcinfo -p localhost
3. Open required ports in firewall. Edit /etc/sysconfig/iptables and add:
-A RH-Firewall-1-INPUT -p udp --dport 111 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp --dport 111 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp --dport 841 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 841 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp --dport 842 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 842 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp --dport 843 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 843 -j ACCEPT
# service iptables restart
4. Setup NIS domain name - edit /etc/sysconfig/network and add:
NISDOMAIN="internal"
5. Initialize NIS maps:
/usr/lib/yp/ypinit -m
6. Secure NIS - permit only trusted networks. You may allow only specified subnets using iptables (i.e. by adding -s 192.168.0.0/24 to the portmap and NIS ports) or by editing /var/yp/securenets and including permitted networks in following format:
255.255.255.0 192.168.0.0
7. Start services and include them in rc3.d scripts:
# service portmap start
# service ypserv start
# chkconfig portmap on
# chkconfig ypserv on
You may include yppasswdd and ypxfrd as well if you need them.
UPDATING NIS MAPS:
# cd /var/yp; make
NIS CLIENT SETUP:
Execute:
# authconfig --update --nisdomain=internal --nisserver=nis.example.com --enablenis
Or:
# authconfig-tui
Finally make sure that ypbind is running and it's added to rc3.d services:
# service ypbind start
# chkconfig ypbind on
VIEWING NIS MAPS:
On the client:
# getent <mapname>
# getent passwd
On any allowed host:
# ypcat -d internal -h nis.example.com <mapname>
# ypcat -d internal -h nis.example.com passwd
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.
