Linux, sar serves to log and evaluate a variety of information regarding system activity. With performance problems, sar also permits retroactive analysis of the load values for various sub-systems (CPUs, memory, disks, interrupts, network interfaces and so forth) and limitation of problems in this manner.
As noted, sar is a component of the sysstat package, which is already contained in numerous distribution files and can be easily installed, depending on the distribution file, either by
yum install sysstat or apt-get install sysstat. Generally at the same time, the cron jobs will be created in /etc/cron.d/sysstat.Functional Approach of Logging
sa1 and sa2 will store the recorded data in the directories, /var/log/sa/ (RHEL/CentOS) or /var/log/sysstat/ (Debian). The data will be retained for a week retroactively in the default configuration. This duration can be increased to 28 days (in /etc/sysconfig/sysstat under RHEL/CentOS or in /etc/sysstat/config under Debian 4.0 and /etc/sysstat/sysstat under Debian 5.0).
Activating sar Logging in Debian: To activate automatic logging under Debian, the "ENABLED" parameters must be set to "true" in the /etc/default/sysstat file. This parameter has been set to "false" by default.
Here is an example of this:
[root@testserver ~]# cat /etc/sysconfig/sysstat # How long to keep log files (days), maximum is a month HISTORY=7 [root@testserver ~]# cat /etc/cron.d/sysstat # run system activity accounting tool every 10 minutes */10 * * * * root /usr/lib64/sa/sa1 1 1 # generate a daily summary of process accounting at 23:53 53 23 * * * root /usr/lib64/sa/sa2 -A [root@testserver ~]# ls -l /var/log/sa/ total 8952 -rw-r--r-- 1 root root 410352 May 18 23:50 sa18 -rw-r--r-- 1 root root 410352 May 19 23:50 sa19 -rw-r--r-- 1 root root 410352 May 20 23:50 sa20 -rw-r--r-- 1 root root 410352 May 21 23:50 sa21 -rw-r--r-- 1 root root 410352 May 22 23:50 sa22 -rw-r--r-- 1 root root 410352 May 23 23:50 sa23 -rw-r--r-- 1 root root 410352 May 24 23:50 sa24 -rw-r--r-- 1 root root 410352 May 25 23:50 sa25 -rw-r--r-- 1 root root 253712 May 26 14:40 sa26 -rw-r--r-- 1 root root 611085 May 17 23:53 sar17 -rw-r--r-- 1 root root 611129 May 18 23:53 sar18 -rw-r--r-- 1 root root 611127 May 19 23:53 sar19 -rw-r--r-- 1 root root 611127 May 20 23:53 sar20 -rw-r--r-- 1 root root 611085 May 21 23:53 sar21 -rw-r--r-- 1 root root 611100 May 22 23:53 sar22 -rw-r--r-- 1 root root 611085 May 23 23:53 sar23 -rw-r--r-- 1 root root 611085 May 24 23:53 sar24 -rw-r--r-- 1 root root 611125 May 25 23:53 sar25 [root@testserver ~]#
Displaying the recorded data using sar
Limiting the Display Period
sar can display either the data for the current day (which does not require any special parameters) or the data for a specific day (such as with the
-f /var/log/sa/sa21 parameter).
The query period can be further limited by the following parameters:
-s [ hh:mm:ss ]- sets the starting time (such as-s 07:30:00); if a specific time is not specified, 08:00:00 will be used as the default starting time.-s [ hh:mm:ss ]- sets the ending time (such as-s 19:30:00); if a specific time is not specified, 18:00:00 will be used as the default ending time.
Parameters for Various Sub-systems
Here are several examples for displaying various values (the values originated on a system using CentOS 4.7 with sysstat version 5.0.5).
Displaying the CPU Load: sar -P ALL
The values for all CPUs (
-P ALL) will be displayed starting from the 25th of the current month (-f /var/log/sa/sa25).[root@testserver ~]# sar -P ALL -f /var/log/sa/sa25 Linux 2.6.9-023stab048.6-smp (testserver.thomas-krenn.com) 05/25/09 00:00:01 CPU %user %nice %system %iowait %idle 00:10:01 all 9.63 0.00 3.81 6.20 80.36 00:10:01 0 8.69 0.00 3.63 7.18 80.50 00:10:01 1 9.28 0.00 3.96 4.47 82.29 00:10:01 2 10.22 0.00 3.86 6.31 79.62 00:10:01 3 9.84 0.00 3.66 6.91 79.59 00:10:01 4 9.86 0.00 3.94 5.28 80.92 00:10:01 5 9.97 0.00 3.84 6.37 79.81 00:10:01 6 9.90 0.00 4.04 7.21 78.85 00:10:01 7 9.32 0.00 3.54 5.83 81.32 [...] Average: all 9.21 0.00 1.68 0.27 88.84 Average: 0 9.03 0.00 1.70 0.31 88.97 Average: 1 9.20 0.00 1.67 0.25 88.88 Average: 2 9.45 0.00 1.70 0.28 88.56 Average: 3 9.84 0.00 1.68 0.26 88.22 Average: 4 9.23 0.00 1.68 0.26 88.84 Average: 5 9.05 0.00 1.68 0.27 89.00 Average: 6 8.90 0.00 1.68 0.29 89.14 Average: 7 8.97 0.00 1.66 0.28 89.10 [root@testserver ~]#
Displaying the RAM Load: sar -r
The RAM values (
-r) for the current day will be displayed here. A value of approximately 100 for the percentage of memory used is thoroughly positive (if swapping is not required). See also the Operating System Caches section of the RAID Controller and Hard Disk Cache Settings article.[root@testserver ~]# sar -r Linux 2.6.9-023stab048.6-smp (testserver.thomas-krenn.com) 05/26/09 00:00:01 kbmemfree kbmemused %memused kbbuffers kbcached kbswpfree kbswpused %swpused kbswpcad 00:10:01 67248 16292680 99.59 42320 12502420 2047648 628 0.03 0 00:20:01 129776 16230152 99.21 47020 12527100 2047648 628 0.03 0 [...] 14:50:01 638680 15721248 96.10 158392 6953128 2047648 628 0.03 0 15:00:01 646272 15713656 96.05 159880 6966980 2047648 628 0.03 0 15:10:01 59784 16300144 99.63 132044 6565036 2047648 628 0.03 0 Average: 554290 15805638 96.61 124889 10992802 2047648 628 0.03 0 [root@testserver ~]#
Displaying the Load Average: sar -q
The average load values (
-q) for the current day will be displayed here.[root@testserver ~]# sar -q Linux 2.6.9-023stab048.6-smp (testserver.thomas-krenn.com) 05/26/09 00:00:01 runq-sz plist-sz ldavg-1 ldavg-5 ldavg-15 00:10:01 0 590 1.62 1.89 1.21 00:20:01 11 574 0.24 0.63 0.86 [...] 15:10:01 7 671 2.36 2.26 2.03 15:20:01 9 651 1.85 1.96 1.99 Average: 7 600 1.02 1.04 1.00 [root@testserver ~]#
Displaying the I/O Transfer Rate: sar -b
The I/O transfer rates (
-r) for the current day will be displayed here.[root@testserver ~]# sar -b Linux 2.6.9-023stab048.6-smp (testserver.thomas-krenn.com) 05/26/09 00:00:01 tps rtps wtps bread/s bwrtn/s 00:10:01 402.21 197.20 205.00 35133.80 27616.04 00:20:01 66.61 56.36 10.24 2034.96 288.93 [...] 15:20:01 72.43 6.54 65.89 176.29 2720.35 15:30:01 73.28 6.08 67.20 399.04 3516.21 Average: 40.21 5.57 34.64 585.00 1561.78 [root@testserver ~]#
tps - Total number of transfers per second that were issued to physical devices. A transfer is an I/O request to a physical device. Multiple logical requests can be combined into a single I/O request to the device. A transfer is of indeterminate size
rtps - Total number of read requests per second issued to physical devices
wtps - Total number of write requests per second issued to physical devices
bread/s - Total amount of data read from the devices in blocks per second. Blocks are equivalent to sectors with 2.4 kernels and newer and therefore have a size of 512 bytes. With older kernels, a block is of indeterminate size.
bwrtn/s - Total amount of data written to devices in blocks per second.
Displaying the Network Statistics: sar -n DEV
The statistical network values (
-n) for the current day will be displayed here.[root@testserver ~]# sar -n DEV Linux 2.6.9-023stab048.6-smp (testserver.thomas-krenn.com) 05/26/09 00:00:01 IFACE rxpck/s txpck/s rxbyt/s txbyt/s rxcmp/s txcmp/s rxmcst/s 00:10:01 lo 0.82 0.82 177.69 177.69 0.00 0.00 0.00 00:10:01 eth0 31.56 40.21 4537.41 35891.07 0.00 0.00 0.00 00:10:01 eth1 4876.29 9919.22 451754.61 14927283.09 0.00 0.00 0.00 00:10:01 venet0 52.88 44.19 46547.68 15279.15 0.00 0.00 0.00 [...] 15:30:01 lo 0.82 0.82 176.68 176.68 0.00 0.00 0.00 15:30:01 eth0 113.08 155.70 17825.90 188643.77 0.00 0.00 0.00 15:30:01 eth1 634.80 1268.92 58495.76 1888004.02 0.00 0.00 0.00 15:30:01 venet0 189.86 147.08 213164.21 42532.10 0.00 0.00 0.00 Average: lo 0.82 0.82 177.10 177.10 0.00 0.00 0.00 Average: eth0 56.42 78.90 9104.66 94428.28 0.00 0.00 0.00 Average: eth1 281.59 559.55 25919.74 830592.96 0.00 0.00 0.00 Average: venet0 87.26 64.75 99974.13 14933.05 0.00 0.00 0.00 [root@testserver ~]#
Displaying All Values
The collective values for all devices (CPU, RAM, etc.) can be displayed using
sar -A.
No comments:
Post a Comment