Problem
How to change the DMP I/O policy and monitor for performance
Solution
| This article is a part of a set on troubleshooting volume performance. Click here to start at the beginning: https://www.veritas.com/docs/000087750 |
Table of Contents
Introduction
Determining the current I/O policy
Changing the I/O policy
Measuring DMP I/O performance using vxdmpadm iostat
Introduction
(Back to top)
When troubleshooting storage performance, review the DMP I/O policy for the disks. In some cases, switching to a different I/O policy may improve performance. For active/active arrays, "MinimumQ" (also known as "Least Queue Depth") is the default I/O policy, and it often provides the best I/O performance with little configuration required. The optimal I/O policy will always depend on the environment and the type of I/O.
Determining the current I/O policy
(Back to top)
Follow these steps to determine the current DMP I/O policy and change it, if needed:
- Use vxdmpadm listenclosure all to find the names of all attached disk enclosures (Figure 1).
- Use vxdmpadm getattr enclosure <enclosure_name> iopolicy to determine the DMP I/O policy of a specific enclosure (Figure 2).
In Figure 1, two enclosures are listed. "Disk" is a generic ASL that was loaded for the internal (non-SAN) disks. The name of the SAN disk array "ams_wms0."
Figure 1 - Using vxdmpadm to generate a list of available disk enclosures
Syntax: vxdmpadm listenclosure all Example, with typical output: # vxdmpadm listenclosure all |
Figure 2 - Using vxdmpadm to determine the iopolicy of a given disk array
Syntax: vxdmpadm getattr enclosure <enclosure_name> iopolicy Example, with typical output: # vxdmpadm getattr enclosure ams_wms0 iopolicy |
Changing the I/O policy
"Specifying the DMP I/O policy" (from the Veritas Storage Foundation 6.0.1 Administrators Guide for Solaris)
https://sort.Veritas.com/public/documents/sfha/6.0.1/solaris/productguides/html/sf_admin/ch09s07s16.htm
- Use vxdmpadm listenclosure all to find the names of all attached disk enclosures (Figure 1, in the previous section).
- Use vxdmpadm setattr enclosure <enclosure_name> iopolicy=<iopolicy> to specify a new I/O policy (Figure 3).
Figure 3 - Using vxdmpadm to change the iopolicy for a disk array
Syntax: vxdmpadm setattr enclosure <enclosure_name> iopolicy=<iopolicy> Example, with typical output: # vxdmpadm setattr enclosure ams_wms0 iopolicy=balanced Note: Vxdmpadm getattr now shows that the current I/O policy is "Balanced."
|
Measuring DMP I/O performance using vxdmpadm iostat
(Back to top)
Vxdmpadm includes a I/O performance measuring utility that can be used to track performance before and after the DMP I/O policy has been changed (Figure 4).
"Examples of using the vxdmpadm iostat command" (from the Veritas Storage Foundation 6.0 Administrators Guide for Solaris)\
https://sort.Veritas.com/public/documents/sfha/6.0.1/solaris/productguides/html/sf_admin/ch09s07s11s01.htm
Figure 4 - Using vxdmpadm iostat to generate performance statistics for all available paths
Syntax:
Example, with typical output: # vxdmpadm -uh -z iostat show all interval=30
Note: Using the "-z" switch causes
vxdmpadm to omit paths that have zero I/O during each interval. The first sample is a cumulative of all I/O statistics since vxmpadm iostat was reset. A blank space is added between each sample.
cpu usage = 36us per cpu memory = 282624b |
Was this content helpful?
Translated Content
Please note that this document is a translation from English, and may have been machine-translated. It is possible that updates have been made to the original version after this document was translated and published. Veritas does not guarantee the accuracy regarding the completeness of the translation. You may also refer to the English Version of this knowledge base article for up-to-date information.