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Subject: Re: fsync(2) and on-disk write-back cache
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  On FreeBSD, BIO_FLUSH is used to communicate between the 
filesystem./buffer cache's desire to flush out and the low level cache.

> I may be wrong, but it seems to me that the actual cache flush on the
> disk is handled at a very low level - in the drivers.
>
> At least I'm pretty certain that e.g. the ahci code sends flush commands
> to the disks.
>
> --
> Gary Jennejohn
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