dirty_ratio & dirty_background_ratio settings with huge memory

Hi,
I've got cutomer with really huge RAM, now it's:
             total       used       free     shared    buffers     cached
Mem:       3102111    3052596      49515     208801        992    2961185
-/+ buffers/cache:      90418    3011693
Swap:         8191          1       8190

(free -m)

and before it was twice more (6TB).

and trying to figure out how to set dirty_ratio & dirty_background_ratio
parameters. Even for normal sized server those default sizes are to high,
but now would be ridiculously huge, respectively 1,24TB and 300GB. 
I'm thinking about 1 percent for dirty_ratio and not using
dirty_background_ratio because it's not possible to set it below 1% but to
set dirty_background_bytes instead to about 1-2GB.
Maybe someone has got other experience with RAM of this size and those
settings?





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