I am reaching out to inquire about the performance of our local storage setup. Currently, I am conducting tests using NVMe disks; however, the results appear to be underwhelming.

In terms of my setup, I have recently incorporated two NVMe disks into my compute node. These disks have been configured as RAID1 under md127 and subsequently mounted at /var/lib/nova/instances [1]. During benchmarking using the fio tool within this directory, I am achieving approximately 160,000 IOPS [2]. This figure serves as a satisfactory baseline and reference point for upcoming VM tests.

As the next phase, I have established a flavor that employs a root disk for my virtual machine [3]. Regrettably, the resulting performance yields around 18,000 IOPS, which is nearly ten times poorer than the compute node results [4]. While I expected some degradation, a tenfold decrease seems excessive. Realistically, I anticipated no more than a twofold reduction compared to the compute node's performance. Hence, I am led to ask: what should be configured to enhance performance?

I have already experimented with the settings recommended on the Ceph page for image properties [5]; however, these changes did not yield the desired improvements. In addition, I attempted to modify the CPU architecture within the nova.conf file, switching to Cascade Lake architecture, yet this endeavor also proved ineffective. For your convenience, I have included a link to my current dumpxml results [6].

Your insights and guidance would be greatly appreciated. I am confident that there is a solution to this performance disparity that I may have overlooked. Thank you in advance for your help.