Option to boot from virtualmedia

[SchwarzM]

What would you like to be added:
I would like to discuss if we can add an option to boot from virtual-media instead of network boot.

Why is this needed:
This would decouple the server from any and all boot related network requirements (DHCP relay etc.)

Pro's:

• no more network dependency for booting
• less blackbox as the mount is an api call which can be verified

Con's:

• might be vendor specific
• more bandwidth on oob connection needed

[fwiesel]

I'd like to add, that at least when I looked at it with iDRAC the virtual-media boot translates all IO requests directly into requests to the storage. In case of HTTP it will be HTTP range request with 4k block-size (or even 512 bytes?), which incur some overhead. At least with swift, that was significant and it was much more latency than bandwidth bound. AFAIK all vendors also support NFS as a virtual media source.

Another advantage of virtual-media is that the data is read "on-demand".
With HTTP-Boot, the whole image is loaded, and then booted, while with virtual-media, it only needs to read the kernel and the ramdisk and the rest of the image is read when needed, so it is much less sensitive to unused data.