On Thu, Oct 04, 2018 at 01:33:12PM -0500, Eric Sandeen wrote: > On 10/4/18 12:58 PM, Ilya Dryomov wrote: > > rbd devices report the following geometry: > > > > $ blockdev --getss --getpbsz --getiomin --getioopt /dev/rbd0 > > 512 > > 512 > > 4194304 > > 4194304 dm-thinp does this as well. THis is from the thinp device created by tests/generic/459: 512 4096 65536 65536 And I've also seen some hardware raid controllers do this, too, because they only expose the stripe width in their enquiry page rather than stripe unit and stripe width. IOWs, this behaviour isn't really specific to Ceph's rbd device, and it does occur on multi-disk devices that have something layered over the top (dm-thinp, hardware raid, etc). As such, I don't think there's a "one size fits all" solution and so someone is going to have to tweak mkfs settings to have it do the right thing for their storage subsystem.... Indeed, does Ceph really needs 4MB aligned filesystem IO? What performance benefit does that give over setting iomin=PAGE_SIZE and ioopt=0? (i.e mkfs.xfs -d sunit=0,swidth=0 or just mounting with -o noalign) Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
