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Troubleshooting Disk Performance (Doc ID 1010680.1)

Last updated on JULY 07, 2023

Applies to:

Solaris Operating System - Version 8 to 11.4 [Release 8.0 to 11.0]
All Platforms

Purpose

This document highlights some of the needed steps when determining if an issue is the result of poor disk performance. If it is, this document details what data must be collected to help demonstrate and isolate the issue.

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Performance issues rarely resolve easily.  This is because poor performance can be caused by many issues unrelated to disks. For example, a disk performs as well as the applications ask of it. So, a slow application may mislead administrators and users to believe a disk performance issue exists. The best method in any troubleshooting process is to eliminate, as much as possible, the potential performance-limiting factors.

For example, review the layers involved in a simple UFS filesystem on a disk:

  1. Physical Disk.

    1. SCSI Disk
    2. Fibre Channel (FC) Disk
    3. SSD (Solid State Disk)

  2. LUN or iSCSI LUN, if it is an array.

  3. Host Bus Adaptor (HBA).

  4. HBA Driver.

  5. sd/sdd driver.

  6. Filesystem; ufs, zfs, vxfs, etc

  7. Application performing I/O to the filesystem.

These are some of the layers involved in the path of a single I/O, yet it is not exactly comprehensive.

This document expects you can read iostat outputs. Refer to the iostat main page for a description.

Troubleshooting Steps

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