[gpfsug-discuss] mmfsd write behavior

[Sven Oehme]

I am not sure what exactly you are looking for but all blockdevices are
opened with O_DIRECT , we never cache anything on this layer .

On Thu, Sep 7, 2017, 7:11 PM Aaron Knister <aaron.s.knister at nasa.gov> wrote:

> Hi Everyone,
>
> This is something that's come up in the past and has recently resurfaced
> with a project I've been working on, and that is-- it seems to me as
> though mmfsd never attempts to flush the cache of the block devices its
> writing to (looking at blktrace output seems to confirm this). Is this
> actually the case? I've looked at the gpl headers for linux and I don't
> see any sign of blkdev_fsync, blkdev_issue_flush, WRITE_FLUSH, or
> REQ_FLUSH. I'm sure there's other ways to trigger this behavior that
> GPFS may very well be using that I've missed. That's why I'm asking :)
>
> I figure with FPO being pushed as an HDFS replacement using commodity
> drives this feature has *got* to be in the code somewhere.
>
> -Aaron
>
> --
> Aaron Knister
> NASA Center for Climate Simulation (Code 606.2)
> Goddard Space Flight Center
> (301) 286-2776
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