Kbase 20457: Using -vmtune and -maxrandwrt on AIX
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
07/02/2011 |
|
Status: Verified
GOAL:
How the use of the maxrandwrt parameter (of vmtune) can help write performance if using syncd on AIX instead of -directio.
GOAL:
Using the maxrandwrt parameter on AIX for Progress performance
FACT(s) (Environment):
IBM AIX
Progress 8.x
Progress 9.x
FIX:
The maxrandwrt parameter can be changed with the -W option from vmtune. It specifies a threshold (in 4KB pages) for random writes to accumulate in RAM before these pages are sync'd to disk via a write-behind algorithm. This threshold is on a per file basis.
The -W maxrandwrt option is only available in AIX Version 4.1.3 and later. The default value of maxrandwrt is 0, which disables random write-behind. Applications that make heavy use of random writes can get better performance due to less of a dependence on the syncd daemon to force writes out to disk.
Don't confuse this with "write back cache" (where it is possible to get conflicting records). It is in "write back cache" that the OS and/or a disk controller lies about what really happens.
This is a suggested change and is not supported by Progress Software Corporation. This is a kernel modification supported by IBM Corporation.