Configdrive can't be bigger than 64MB

[Lucas Alvares Gomes]

When Nova generates a configdrive with the "iso9660" format (default) it doesn't contain a specific size. Only when the format is "vfat" the configdrive will be 64MB[1] and that's for legacy reasons[2].

Right now IPA is hardcoding the size of the configdrive partiton on 64MB[3] we need to make it flexible so that if a configdrive generate with the "iso9660" format is bigger than 64MB we don't break IPA.

[1] https://github.com/openstack/nova/blob/master/nova/virt/configdrive.py#L120-L123
[2] http://docs.openstack.org/user-guide/content/enable_config_drive.html#config_drive_format
[3] https://github.com/openstack/ironic-python-agent/blob/master/ironic_python_agent/shell/copy_configdrive_to_disk.sh#L62

[Mario Villaplana (mario-villaplana-j)]

I have a fix up in my fork that looks like it works:

https://github.com/supermari0/ironic-python-agent/commit/bf3349f4c9a5696a280d2665a0c5733f1aa12f5f

It seems like depending on the hardware, though, that I sometimes get this message when creating the partition:

"Warning: The resulting partition is not properly aligned for best performance."

This happens when using a small configdrive (<1MB), when the code creates a 1 MB partition.

Any ideas for how to better calculate an optimal alignment before creating the partition? I thought partitioning in increments of 1MB would always be considered "optimal" but apparently I'm wrong.

[Jay Faulkner (jason-oldos)]

Consensus of project team on vPTG bug triage call is:
* passing around >64MB blobs is a bad idea
* any use case that needs >64MB files should bootstrap into real config management