Oracle provides a collection of scripts that gather and store metrics for CPU, memory, disk, and network usage. The OSWatcher tool suite automates the gathering of statistics using tools such as top, vmstat, iostat, mpstat, netstat, and traceroute.
The general file format for the oswiostat data is: [node_name]_iostat_YY.MM.DD:HH24.dat
These files will contain output from the ‘iostat’ command that is obtained and archived by OSWatcher at specified intervals. These files will only exist if ‘iostat’ is installed on the OS and if the oswbb user has privileges to run the utility. Please keep in mind that what gets reported in iostat may be different depending upon you platform. You should refer to your OS iostat man pages for the most accurate up to date descriptions of these fields.
The iostat command is used for monitoring system input/output device loading by observing the time the physical disks are active in relation to their average transfer rates. This information can be used to change system configuration to better balance the input/output load between physical disks and adapters.
The iostat utility is fairly standard across UNIX platforms, but really only useful for those platforms that support extended disk statistics: AIX, Solaris and Linux. Also each platform will have a slightly different version of the iostat utility. You should consult your operating system man pages for specifics. The sample provided below is for Solaris.
oswbb runs the iostat utility at the specified interval and stores the data in the oswiostat subdirectory under the archive directory. The data is stored in hourly archive files. Each entry in the file contains a timestamp prefixed by *** embedded in the iostat output. Notice there is one entry for each timestamp.
Sample iostat file produced by oswbb:
extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 0.3 0.0 2.1 0.0 0.0 3.4 0.8 0 0 c0t0d0 0.0 2.1 0.1 12.9 0.0 0.0 0.6 0.4 0 0 c0t2d0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 fd0 2.9 1.2 240.8 1.5 0.0 0.1 0.0 13.3 0 5 c1t0d0 1.1 0.8 18.0 8.8 0.0 0.0 0.1 5.9 0 1 c1t1d0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c0t1d0
Field Descriptions
The iostat output contains summary information for all devices.
| Field | Description |
|---|---|
| r/s | Shows the number of reads/second |
| w/s | Shows the number of writes/second |
| kr/s | Shows the number of kilobytes read/second |
| kw/s | Shows the number of kilobytes written/second |
| wait | Average number of transactions waiting for service (queue length) |
| actv | Average number of transactions actively being serviced |
| wsvc_t | Average service time in wait queue, in milliseconds |
| asvc_t | Average service time of active transactions, in milliseconds |
| %w | Percent of time there are transactions waiting for service |
| %b | Percent of time the disk is busy |
| device | Device name |
What to look for
– Average service times greater than 20msec for long duration.
– High average wait times.