Xiao Ni <xni@xxxxxxxxxx> wrote: > Because it can be reproduced easily in your environment. Can you try > with the latest upstream kernel? If the problem doesn't exist with > latest upstream kernel. You can use git bisect to find which patch can > fix this problem. I just tried the upstream. I get almost the same result with 1G ramdisks. Without RAID (writing to /dev/ram0) READ: IOPS=15.8M BW=60.3GiB/s WRITE: IOPS= 6.8M BW=27.7GiB/s RAID1 (writing to /dev/md/test) READ: IOPS=518K BW=2028MiB/s WRITE: IOPS=222K BW= 912MiB/s > > We are actually executing hundreds of VMs on our hosts. The problem > > is that when we use RAID1 for our enterprise NVMe disks, the > > performance degrades very much compared to using them directly; it > > seems we have the same bottleneck as the test described above. > > So those hundreds VMs run on the raid1, and the raid1 is created with > nvme disks. What's /proc/mdstat? At the moment we do not use raid1 due to this performance issue. Since the machines are in production, I can not change their disk layout. If I find the opportunity, I will set up raid1 on real disks and report the contents of /proc/mdstat. Thanks, Ali
