I have more of a principle question:
can I (and if so, how?) control the HD access so that, in the extreme case, I can make the OS write only to the cache in stead of the HD?
For example, using ext3:
I have as mount options commit=10000,noatime
and set the hdparms so that the HD spins down. So, from this, I understand that the OS writes into the cache, and the cache is synchronized every 10000ms.
Still, the HD behaves as if it has its own life :-))
Assuming that all processes use the filesystem to write to the HD, shouldn’t I then be able to fully control the access to the HD?
How can I get FULL control of the HD in terms of when it is accessed and how often?
What I have used already is
*tuning pdflush by setting varous things in /prov/sys/vm:
echo 5 > /proc/sys/vm/laptop_mode
echo 40 > /proc/sys/vm/dirty_ratio
echo 1 > /proc/sys/vm/dirty_background_ratio
echo 10000 > /proc/sys/vm/dirty_writeback_centisecs
*controlling kjournald using the mount options commit and noatime.
but even with aggressive settings, if I set
sysctl vm.block_dump=1
I can see that there are all sorts of wake-ups and WRITEs!!
This leads me to believe that there is more to do to gain full control…