<div dir="ltr">Great, I will do that. Thank you for all your help!</div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Apr 24, 2019 at 6:22 PM Mike Snitzer <<a href="mailto:snitzer@redhat.com">snitzer@redhat.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On Wed, Apr 24 2019 at 5:27pm -0400, Mike Snitzer <<a href="mailto:snitzer@redhat.com" target="_blank">snitzer@redhat.com</a>> wrote: > > On Wed, Apr 24 2019 at 10:46am -0400, > Ryan Norwood <<a href="mailto:ryan.p.norwood@gmail.com" target="_blank">ryan.p.norwood@gmail.com</a>> wrote: > > > On Wed, Apr 24, 2019 at 9:08 AM Ryan Norwood <[1]<a href="mailto:ryan.p.norwood@gmail.com" target="_blank">ryan.p.norwood@gmail.com</a>> > > wrote: > > > > Thank you for your help. > > You are correct, it appears that the problem occurs when there is a RAID > > 5 or RAID 50 volume beneath VDO. > > NAME KNAME RA SIZE ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC > > RQ-SIZE SCHED WSAME > > sdh > > sdh 128 977.5G 0 512 0 512 512 128 > > deadline 0B > > +-sed6 > > dm-6 128 977.5G 0 512 0 512 512 128 > > 0B > > +-md127 > > md127 12288 5.7T 0 1048576 6291456 512 512 128 > > 0B > > +-vdo_data > > dm-17 128 5.7T 0 1048576 6291456 512 512 128 > > 0B > > +-vdo > > dm-18 128 57.3T 0 4096 4096 4096 4096 128 > > 0B <snip> > > /sys/block/dm-18/queue/max_hw_sectors_kb:4 > > /sys/block/dm-18/queue/max_sectors_kb:4 These are getting set as a side-effect of MD raid imposing the need for merge_bvec (in the context of RHEL7.x only, not upstream) otherwise it goes conservative and forces the IO to be contrained to a single page, please see: drivers/md/dm-table.c:dm_set_device_limits() at the end: /* * Check if merge fn is supported. * If not we'll force DM to use PAGE_SIZE or * smaller I/O, just to be safe. */ if (dm_queue_merge_is_compulsory(q) && !ti->type->merge) blk_limits_max_hw_sectors(limits, (unsigned int) (PAGE_SIZE >> 9)); With MD raid in the IO stack, dm_queue_merge_is_compulsory() will return true, so the VDO target not providing ti->type->merge causes this issue. Please file a BZ at <a href="http://bugzilla.redhat.com" rel="noreferrer" target="_blank">bugzilla.redhat.com</a> against VDO and I'll continue to work with the VDO developers to get this fixed for you for RHEL7.5, etc. Thanks, Mike </blockquote></div>