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Cisco 7800 Series Media Convergence Servers

Field Notice: FN - 63112 - MCS-7816-H3 Hard Drive Write Cache Setting Can Cause High CPU on VOS-based Systems

Cisco - Field Notice: FN - 63112 - MCS-7816-H3 Hard Drive Write Cache Setting Can Cause High CPU on VOS-based Systems

April 29, 2008


NOTICE:

THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE FIELD NOTICE OR MATERIALS LINKED FROM THE FIELD NOTICE IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS FIELD NOTICE AT ANY TIME.

Revision History

Revision Date Comment
1.0 29-APR-2008 Initial Public Release

Products Affected

Products Affected Comments
MCS-7816-H3 VOS Systems Only. Windows OS is NOT affected.

Problem Description

On MCS-7816-H3 servers, with BIOS versions before Version W04 Release Date: 04/03/2008, the Hard Drive Write Cache setting did not take effect. The end result was the drive's write cache was disabled.

Voice Operating System
On Voice Operating System (VOS) based platforms, disabling the Hard Drive Write Cache has a negative effect on hard drive performance and can cause the CPU on the server to plateau above 90%. This causes resource starvation for other services and can lead to system outages.

Windows Operating System
On Windows-based platforms, the Hard Drive Write Cache is enabled independently of the BIOS, therefore no performance degradation exists. This issue is not present on Windows Operating Systems.

Background

Enabling Hard Drive Write Cache can be a desirable setting that improves hard drive performance.

Most other MCS server platforms have the Hard Drive Write Cache enabled by default.

Problem Symptoms

Voice Operating System
An MCS-7816-H3 running a VOS-based Application like Cisco Unified CM 6.1 may experience a high CPU condition where IOWait is the service exhausting most of the resources. It can ultimately result in resource starvation and service outages. This can happen with minimal load to the system in terms of users, phones, and so on.

Windows Operating System
On Windows-based platforms, the Hard Drive Write Cache is enabled independently of the BIOS. Therefore, no performance degradation exists. This issue is not present on Windows Operating Systems.

Workaround/Solution

Voice Operating System
1. The permanent solution is to upgrade to a version that contains a BIOS update. At the time of this writing, there is no version yet available on Cisco.com with the BIOS update. Please use the Product Subscription Tool (registered Cisco.com users only) to receive notification when a new version has been posted to Cisco.com. Once a new version is released, check the Bug Toolkit (registered customers only) to make sure the caveat is resolved in that version.

2. A suitable workaround which can be used until a fixed version is available on Cisco.com is to apply the following COP file, which does not contain a BIOS upgrade, but instead contains a utility that enables the Hard Drive Write Cache independently.

1. Download the file "ciscocm.CSCsm83603EnableCache7816-1.1.cop.sgn" from Cisco Unified Communications Manager Utilities (registered customers only)
2. Read through the readme file, called "ciscocm_MCS7816EnableWriteCache_README_1-1.txt"
3. Install the COP file according the Software Upgrade instructions in the product documentation for the Application running on the server.

Windows Operating System
On Windows-based platforms, the Hard Drive Write Cache is enabled independently of the BIOS, therefore no performance degradation exists. This issue is not present on Windows Operating Systems. A workaround and solution are not required on Windows-based platforms since the issue is not present on Windows Operating Systems.

As of approximately April 22, 2008, new products that were manufactured under ECO E093123 have the BIOS upgrade already and are guaranteed to be free of this problem.

DDTS

To follow the bug ID link below and see detailed bug information, you must be a registered customer and you must be logged in.

DDTS Description
CSCsm83603 (registered customers only) MCS 7816-H3 servers have performance issues showing High % I / 0 Wait

How To Identify Hardware Levels

The corrected BIOS Version is: W04
Release Date: 04/03/2008

Note that if the workaround is applied, the BIOS version will not change because there is no BIOS update in the COP file.

MCS-7816-H3 with this BIOS version will ship under ECO E093123, which began shipping approximately April 22, 2008.

How to Check the BIOS Version
1. Reboot the server
2. During a system Boot the BIOS Version information is the first thing that is printed to the screen after the HP Splash Screen.
3. If you miss this, to go into the BIOS menu to check the BIOS version, press the F9 key during the reboot to enter the ROM Based Setup Utility (RBSU).
4. In the RBSU, the BIOS version is printed in a System Information box on the right side of the screen.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

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