Le 28/12/2015 19:22, Simon Hobson a écrit :
> The cache gets written out when the background system processes clean up and write the dirty pages out to disk. How long this takes depends on tuneable kernel parameters and how busy the system is. If the system, and in particular the storage, is otherwise idle then IIRC your small file will get written almost instantly. If the system is really busy, with a large dirty cache, then it'll take a lot longer.
That's the logic one would naively expect but I'm not sure of it.
I'm afraid the data remains in the cache and not backed-up to disk
until some process needs room in the cache. You can do the experiment of
writing data to a usb memory stick and then wait long after the light
has stopped blinking. Then you can either sync or umount the device and
it will blink again for some time before the command returns.
Didier