Firmware Assisted Dump sysdump

Firmware Assisted Dump

 

Firmware Assisted Dump

 
 

Technote (FAQ)


Question

This document describes the firmware assisted dump option for AIX system dumps.

Answer


The firmware assisted dump option was added in AIX 6.1 to improve the system dump facility for servers that boot from a SAN or virtual SCSI disks, but it will also work with servers that boot from internal disks. On AIX 6.1 and below, the default dump type is traditional. On AIX 7.1, the default type is firmware assisted. A traditional system dump is written immediately after a server crashes. A firmware assisted dump is written when the server is booting, after device discovery.

The firmware assisted dump option can be enabled with the sysdumpdev command, and is the default setting for AIX 7.1. This option might be beneficial for systems that are experiencing dump failures with a -3 dump status code, as reported by the sysdumpdev -L command. A -3 dump status means that the dump failed or did not start. This can happen because the AIX dump drivers are unable to communicate with the dump device, but also if the dump process is manually interrupted by an operator in an attempt to boot the server as quickly as possible. If the dump is failing for some reason other than being interrupted by an operator, the firmware assisted dump option is recommended.

Requirements

  • The firmware assisted dump option will only work on POWER6 hardware, and above.
  • The firmware assisted dump option will not work if the default paging device hd6 is used as the dump device. A dedicated logical volume must be configured in to use the firmware assisted dump.

How to Enable the Firmware Assisted Dump

To enable the firmware assisted dump, run the following commands:

sysdumpdev -t fw-assisted
shutdown -Fr


********** AIX Dump Device Settings (sysdumpdev -l) **********
primary /dev/dumplv
secondary /dev/sysdumpnull
copy directory /var/adm/ras
forced copy flag TRUE
always allow dump FALSE
dump compression ON
type of dump traditional

.
I would recommend changing the dump type on this server from "traditional" to "firmware assisted". This is done  as follows:         
.
      # sysdumpdev -t fw-assisted
      # bosboot -ad /dev/ipldevice


        reboot the system..
.
A reboot is needed to fully implement this change.  The advantage of a firmware assisted dump is that the dump is written during system reboot after device discovery.  A traditional dump is written as the server   
goes down.  If there is a problem accessing storage the dump will fail.
.                                                                      
fw-assisted type of dump prerequisite:                                 
.                                                                      
- The dump space should be in the rootvg volume group.                 
- The dump space should not be Mirrored and / or stripped.             
- The dump space should not be the paging space.                       
- Its size should be the value of sysdumpdev -e full load + 10%. 

 




Note that a reboot is required in order to activate the firmware assisted dump.

Note for EMC SAN Boot Systems

If a system boots from an EMC SAN and the dump is failing with a -3 status code, consider the following:
  • EMC Powerpath must be at version 5.7 or later, or version 5.5.0.2 or earlier for both traditional and firmware assisted dumps to work properly. For example, if you have EMC PowerPath 5.5.0.6, both a traditional and firmware assisted dump will fail.
  • To improve the chances of writing a successful dump on a system that boots from an EMC SAN, the firmware assisted dump option is recommended. However, AIX firmware assisted dumps were originally designed to work only with MPIO and SCSI disks. Support for EMC Powerpath was not added until AIX 6100-08 and and 7100-02. If the system is at one of these levels or higher, and if the EMC PowerPath device driver is compatible with the AIX dump facility, then the firmware assisted dump option is recommended.
  • A traditional dump can be used for an EMC SAN boot system, but the firmware assisted dump option is recommended for compatible systems.

Testing the Dump Facility

If system dumps are not completing successfully, the dump facility can be tested to see if the problem can be reproduced. To test the dump facility, shut down all applications such that only AIX is running. Then either force a system dump using the HMC interface (select the Restart command and then select the dump option) or run the following command as root:

sysdumpstart -p

After the system automatically reboots, run the sysdumpstart -L command to check the status of the dump. If the dump is not completing successfully, contact AIX Support for assistance.
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