On Fri, Apr 19 2019 at 10:40am -0400, Ryan Norwood <ryan.p.norwood@xxxxxxxxx> wrote: > We have been using dm-thin layered above VDO and have noticed that our > performance is not optimal for large sequential writes as max_sectors_kb > and max_hw_sectors_kb for all thin devices are set to 4k due to the VDO > layer beneath. > This effectively eliminates the performance optimizations for sequential > writes to skip both zeroing and COW overhead when a write fully overlaps a > thin chunk as all bios are split into 4k which always be less than the 64k > thin chunk minimum. > Is this known behavior? Is there any way around this issue? Are you creating the thin-pool to use a 4K thinp blocksize? If not, I'll have to look to see why the block core's block limits stacking would impose these limits of the underlying data device. > We are using RHEL 7.5 with kernel 3.10.0-862.20.2.el7.x86_64. OK, please let me know what the thin-pool's blocksize is. Thanks, Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
