what's the magic behind the massive write speed performance boost by intel RST drivers up till and including version 11.2.0?
i have done some performance measurements of my application that is extreme heavily writing to the HDD (it is indirectly making FlushFileBuffers getting called in a very thight loop).
the testing has been carried out on different environments and also with different drivers.
the results are:
on environments with above mentioned RST drivers the "overall" application performance is 5 times higher - compared against the other environments that have either:
- HDD running in legacy IDE mode
- AHCI with generic microsoft drivers
- AHCI with intel RST drivers later than 11.2.0
.
now there's one interesting observation:
in windows one can switch OFF the write-cache buffer flushing, e.g. for testing purposes.
with this tweak in place the performance of systems with any driver is identical to those with RST "11.2.0"!
so here comes the question:
due to the very similar performance one could suspect that those older RST drivers are unintentionally also filtering out the FlushFileBuffers.
and hence the performance improvement is rather by accident than by smart driver logic...?
in case it's not: why are the "later" RST drivers (such as 11.7 or 12.9) no longer having such good write performance?
.
PS:
as learned from fernando at http://www.win-raid.com/t25f23-Which-are-the-quot-best-quot-Intel-AHCI-RAID-drivers.html:
- the classic RST drivers (up till 11.2.0) consist of one single driver "iaStor.sys".
- the newer generation of RST drivers consist of "iaStorA.sys" plus an addition "SCSI filter driver".
and in my testing those newer RST drivers no longer show any performance improvements with this one particular application.
