Re: [gpfsug-discuss] mmfsd write behavior

Thanks, Sven. I think my goal was for the REQ_FUA flag to be used in alignment with the consistency expectations of the filesystem. Meaning if I was writing to a file on a filesystem (e.g. dd if=/dev/zero of=/gpfs/fs0/file1) that the write requests to the disk addresses containing data on the

Re: [gpfsug-discuss] mmfsd write behavior

Hi, yeah sorry i intended to reply back before my vacation and forgot about it the the vacation flushed it all away :-D so right now the assumption in Scale/GPFS is that the underlying storage doesn't have any form of enabled volatile write cache. the problem seems to be that even if we set

Re: [gpfsug-discuss] mmfsd write behavior

Hi Sven, Just wondering if you've had any additional thoughts/conversations about this. -Aaron On 9/8/17 5:21 PM, Sven Oehme wrote: Hi, the code assumption is that the underlying device has no volatile write cache, i was absolute sure we have that somewhere in the FAQ, but i couldn't

Re: [gpfsug-discuss] mmfsd write behavior

Thanks Sven. I didn't think GPFS itself was caching anything on that layer, but it's my understanding that O_DIRECT isn't sufficient to force I/O to be flushed (e.g. the device itself might have a volatile caching layer). Take someone using ZFS zvol's as NSDs. I can write() all day log to that

Re: [gpfsug-discuss] mmfsd write behavior

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 wrote: > Hi Everyone, > > This is something that's come up in the past and has recently