AIX 4.3.3 - Mirroring Problems

[charliejb]

We have recently implemented AIX 4.3.3 Mirroring/Striping.

Our applications(Oracle 8i) are write intensive in Overnight batch mode, since implementing mirroring we have seen a 20/30% decrease in system write speed.

When mirroring is removed performance returns to normal.

Are there any AIX settings which we have missed which could cause this problem?

 

[Chapter11]

There's an obscure little detail that can affect this:

the Mirror Write Consistency check uses space on the outer edge of the physical disk as a "log" (sorta like jfslog). If your LV is located further into the disk, you'll have thrashing between that spot and the outer edge as that log is updated.

Solutions are to either turn off that check (bad idea), or to reorg your vg so that LVs that are mirrored prefer the outer edge.

 

[charliejb]

Thanks for the response, but on further investigation I believe our problem may lye with the System paging space and the mirroring performance problems are a result of the increased I/O.

One of the changes in AiX 4.3.3, was now the system deals with paging space setting a parameter "Early/Late".

Does any body know the command to check what the paging is set to (psalloc ?).

Thanks again for your help.

 

[Yegolev]

I'm pretty sure you need to put

export PSALLOC=early

in /etc/environment. You can presumably check with:

print $PSALLOC

If you get nothing, it is not set. IBM Certified -- AIX 4.3 Obfuscation

 

[nam0211]

Hello,

Topas can give the what is the paging you had set for ?