Poor I/O performance on OpenStack block device (OpenStack Centos8:Ussuri)

Vinh Nguyen Duc vinhducnguyen1708 at gmail.com
Thu Jul 7 04:27:21 UTC 2022

I have a problem with I/O performance on Openstack block device HDD.

*Environment:**Openstack version: Ussuri*
- OS: CentOS8
- Kernel: 4.18.0-240.15.1.el8_3.x86_64
- KVM: qemu-kvm-5.1.0-20.el8
*CEPH version: Octopus * *15.2.8-0.el8.x84_64*
- OS: CentOS8
- Kernel: 4.18.0-240.15.1.el8_3.x86_64
In CEPH Cluster we have 2 class:
- Bluestore
- HDD (only for cinder volume)
- SSD (images, cinder volume)
- Ceph-client: 2x10Gbps (bond) MTU 9000
- Ceph-replicate: 2x10Gbps (bond) MTU 9000
- Swapoff
- non LVM

*Issue*When create VM on Openstack using cinder volume HDD, have really
poor performance: 60-85 MB/s writes. And when tests with ioping have high
1.  I have checked the performance between Compute Host (Openstack) and
CEPH, and created an RBD (HDD class) mounted on Compute Host. And the
performance is 300-400 MB/s.
=>  So i think the problem is in the hypervisor
But when I check performance on VM using cinder Volume SSD, the result
equals performance when test RBD (SSD) mounted on a Compute host.
2.  I already have to configure disk_cachemodes="network=writeback"(and
enable rbd cache client) or test with disk_cachemodes="none" but nothing
3.  Push iperf3 from compute host to random ceph host still has 20Gb
4.  Compute Host and CEPH host connected to the same switch (layer2).
Where else can I look for issues?
Please help me in this case.
Thank you.
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