Error Message

 

 

VxFS has a tunable called "lowmem_disable" which is 0 by default.

The recommendation for AIX customers is to disable VxFS lowmem handling, so that AIX VMM will take action in the event of low memory pressure. AIX VMM is more efficient than VxFS as it is LRU based.

This can be set by 

# vxtunefs -D lowmem_disable=1 

 

All VxFS filesystems will need to be unmounted when setting this tunable. Otherwise the following error will be observed:

UX:vxfs vxtunefs: ERROR: V-3-26748: failed to set the specified parameters: The requested resource is busy.
UX:vxfs vxtunefs: ERROR: V-3-26721: unable to update value in the file /etc/vx/vxfssystem
 

It should be noted that if VxFS lowmem handling is disabled, the counter "vxi_mm_lowmem_cnt" will not be used for VxFS.

It is also possible that having max_seqio_extent_size set to 32k on a VxFS filesystem might be too aggressive and this may be contributing to low memory. Veritas would recommend setting this back to the pre VxFS 7.3.1 value of 2048 on the filesystems being used by the application.

# vxtunefs -o max_seqio_extent_size=2048 

To check that the setting is now in place using:

# vxtunefs -p  | grep -i max_seqio

Veritas would recommend implementing the above two settings and monitoring the affected system(s). 

In the event the performance issue persists, please contact Veritas Technical Support for further assistance.

On some Aix 7.1 systems running VxFS 7.3.1 intermittent performance issues have been observed. The main issue observed at the time of the performance issue is that %SYS utilization in the Operating System increases a lot and the application experiences a lack of system resources. Additionally slow reads and writes may be experienced within the application. A workaround of manually freeing the filesystem cache can be done to get around this issue. This involves reducing the value of maxclient which causes AIX to free up pages from filesystem cache. Once the filesystem cache has been freed, maxclient can be reverted back to its original value.

JIRA: STESC-3539