> -----Original Message----- > From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of > Mike Christie > Sent: 17 March 2015 21:27 > To: Nick Fisk; 'Jake Young' > Cc: ceph-users@xxxxxxxxxxxxxx > Subject: Re: tgt and krbd > > On 03/15/2015 08:42 PM, Mike Christie wrote: > > On 03/15/2015 07:54 PM, Mike Christie wrote: > >> On 03/09/2015 11:15 AM, Nick Fisk wrote: > >>> Hi Mike, > >>> > >>> I was using bs_aio with the krbd and still saw a small caching > >>> effect. I'm not sure if it was on the ESXi or tgt/krbd page cache > >>> side, but I was definitely seeing the IO's being coalesced into > >>> larger ones on the krbd > >> > >> I am not sure what you mean here. By coalescing you mean merging > right? > >> That is not the same as caching. Coalescing/merging is expected for > >> both aio and rdwr. > > > > For being able to see caching with aio though, I think you are right > > and there might be a case where can use buffered writes even when > > using O_DIRECT to the rbd device. I am not too familiar with that > > code, so let me ping a person that works here and get back to the list. > > I talked to the AIO person here and confirmed that the code can drop down > to buffered writes. However, if that happens it will then make it still look like > O_DIRECT by making sure writes are written back and pages are invalidated. > > If you want I can send you a patch to also do O_SYNC when doing AIO, so we > can make sure flushes/barriers are also done. > > Send me the iometer workload when you get a chance, so I can test it out > here. Thanks for looking into that, I've had a bit of a busy day today, I will set a krbt+tgt lun up tomorrow and send you the iometer stuff. > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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