Write performance degraded inside virtual guests

Issue

• Observed degraded write performance with the guests.
• The host is a pure ssd setup, with 2 400G intel dc s3700 ssds, hardware raid1.
• Without any virtual guests, it shows ~69k IOPS for read, ~38k IOPS for write
• With only on virtual guest running on the host, the virtual guest shows ~50k IOPS for read, ~11k for write.
• In terms of IOPS, read performance degraded to ~70% and write performance degraded to ~30%.
• Both the host and guest is using deadline as the block scheduler, all using ext4.
• The guest is using virtio-blk