Procedure 7-3 Problem: There Is Excess Disk Activity On My Solaris Platform - Alcatel 5620 Troubleshooting Manual

7 — Troubleshooting Solaris and Windows platforms
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Procedure 7-3 Problem: There is excess disk activity on my Solaris
platform
In a system with memory bottlenecks, there is a lot of disk activity. Much of this activity is
related to swapping processes in and out of main memory. Swapping is detrimental to
performance because it increases activity without contributing to productivity. This
causes sluggish performance.
Swapping occurs when the active parts of the processes need more memory than the
size of actual memory installed. When this happens, some of the memory contents are
copied to disk and replaced by another process. When the portion of memory that was
copied to disk is required, it is reloaded.
This scenario may continue until the system is no longer running any processes and is
spending almost all of its time copying code and data in and out of main memory.
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7-6
Table 7-2 iostat report descriptions
Description
Name of the disk
Reads per second
Writes per second
Reads per second (kb/s)
Writes per second (kb/s)
Average number of transactions waiting for service (queue length)
Average number of transactions actively being serviced (removed from the queue
but are not yet complete)
Average service time in ms
Percentage of time there are transactions waiting for service (non-empty queue)
Percentage of time the disk is busy (transactions in progress)
The %b and svc_t columns are the key fields to determine whether a disk bottleneck
exists. If the average service time (svc_t) is between 30 and 50 ms, and the disk
(%b) is greater than 20% busy, there is a minor disk loading problem. If the service
times exceed 50 ms, the disk is considered disk or I/O bound.
In the example, the sd3 disk showed 90 percent disk activity in the %b column.
Because disk sd3 is busier than disk sd1, disk performance may be enhanced by
moving data from disk sd3 to disk sd1.
Open a command or shell tool.
Alcatel 5620 Service Aware Manager, Release 2.1 R2
May 2005 95-5887-01-00-B