With *SM Mirroring you can run even more safely
(comparing to AIX mirroring),
especially if you set up sequential write mode.
When using AIX mirroring there are more possible
single point failures which can cause 
corruption in you DB or LOG files.

Do your both disks hang on single SCI cable and/or scsi controller?
Failure of this components can cause error in your DB.

Do you have separate controllers?
Even so, crash in AIX/OS or an CPU failure or 
similar failures can corrupt your DB.

Generally:

1) AIX mirroring will try to
do as much as possible in parallel,
which is good for performance but, 
while very good,
not necessarilly best for safety.

2) AIX mirroring is low-level, leaving few components
like controller, bus, cpu, OS not mirrored,
thus an error in this components can 
influence 2 or more I/O operations at once,
possibly causing consistency loss.
*SM mirroring is high-level,
consuming more CPUI/BUS/controller ressources,
because it divides one I/= into 2 or more.
This costs performance, but under circumstances
adds security/dafety.

Juraj Salak 

KEBA AG
Softwareentwicklung Bankautomation
Gewerbepark Urfahr 14 - 16
Postfach 111
A-4041 Linz
Österreich

Tel. ++43/732/7090-7461
Fax ++43/732/730910
e-mail: sal AT keba.co DOT at
www.keba.co.at