Hi everyone,

Happy New Year to all! I hope you all had a great holiday season.

I'm reaching out to share a proposal we've been working on that addresses a performance challenge many enterprises face with ephemeral storage in Nova.

Context: Currently, OpenStack deployments running on NFS-based storage (like NetApp FlexGroups) face a significant performance penalty compared to Ceph RBD due to the QCOW2-over-NFS approach. The hypervisor manages Copy-on-Write operations, which introduces:

• Double filesystem metadata overhead (QCOW2 on top of NFS)
• CPU tax on compute nodes for CoW management
• Slower instance provisioning compared to Ceph's instant cloning

We are planning to implement solution that leverages NetApp's FlexClone technology through the ONTAP REST API to achieve Ceph-like performance while maintaining the operational simplicity of NFS. Essentially, we're offloading the cloning operation to the storage array itself, making instance creation a metadata-only operation (sub-second) with zero data copying.

The implementation involves creating a new NetAppNfs image backend class in nova/virt/libvirt/imagebackend.py that calls the ONTAP REST API's /storage/file/clone endpoint instead of traditional file copy operations.

I'm wondering if anyone has insights into:

• Similar efforts: Has anyone explored or implemented storage-side cloning for other NFS vendors?
• Design concerns: Any architectural red flags with this approach in the Nova driver?
• Security practices: Best approach for managing storage credentials and oslo.privsep integration?
• Community interest: Would this be valuable for other NFS deployments?

This will enable high-performance ephemeral storage from, so I'm curious if others have encountered this limitation and whether there's are any known limitation with this approach.

Thanks in advance for any guidance or suggestions!

Best regards,
Jayaanand.