> the OS doesn't need to know about the multiple paths
For high availability, yes. But for performance, I was *under the
impression* that Linux needs to be fooled into using the multiple
paths (haven't been able to confirm this with end-to-end performance
tests). This is done by LVM or raid-tools striping (RAID 0). *As I
understand it* the "fooling" works as follows - when a striped
volume is detected, the Linux kernel will continue with data
transfers before the previous one finishes. Then the multiple
I/O paths to the DASD will be utilized. Actually the first time
I tried a performance test, I saw a small performance gain, but it
was negligible enough to be noise.
The recently I noticed in make menuconfig the setting:
Multi-device support (RAID and LVM) --->
<M> Multipath I/O support
which is not always on. So I'm hopeful for some serious performance
gains using RAID 0 and a kernel with this setting on. Any comments
from performance guys with a better background on this?
-Mike MacIsaac, IBM [EMAIL PROTECTED] (845) 433-7061
