Re: Could RAM possibly be just 3-4 times faster than bare hdd writes and reads? or, is the Linux kernel doing its 'magic' in the bg? or, ...

[Reco <recoverym4n@enotuniq.net>]

	Hi.

On Wed, Jun 17, 2020 at 05:54:51PM -0400, Michael Stone wrote:
> On Wed, Jun 17, 2020 at 11:45:53PM +0300, Reco wrote:
> > Long story short, if you need a primitive I/O benchmark, you're better
> > with both dsync and nocache.
> 
> Not unless that's your actual workload, IMO. Almost nothing does sync i/o;

Almost everything does (see my previous e-mails). No everything does it
with O_DSYNC, that's true.  Although if it uses sqlite - chances are it
does it with O_DSYNC.


> simply using conv=fdatasync to make sure that the cache is flushed before exiting
> is going to be more representative.

If you're answering the question "how fast is my programs are going to
write there" - sure. If you're answering the question "how fast my
drive(s) actually is(are)" - nope, you need O_DSYNC.

Reco