Comment 3 for bug 1481721

> may it be related with the size of bootstrap image?

Ubuntu based bootstrap image is slightly smaller than CentOS one:

[root@fuel /]# ls -lRh /var/www/nailgun/bootstrap/
/var/www/nailgun/bootstrap/:
total 233M
-rwxr-xr-x. 1 root root 228M Aug 4 08:22 initramfs.img
-rwxr-xr-x. 1 root root 4.7M Aug 4 08:22 linux
drwxr-xr-x. 2 root root 4.0K Aug 4 11:26 ubuntu

/var/www/nailgun/bootstrap/ubuntu:
total 229M
-rwxr-xr-x 1 root root 16M Aug 4 11:24 initramfs.img
-rwxr-xr-x 1 root root 5.6M Jul 29 12:35 linux
-rwxr-xr-x 1 root root 209M Aug 4 11:26 root.squashfs

The problem has nothing to do with the image size.
The tftp server we use, tftpd-hpa, is extremely dumb and spawns a process to handle each client,
so it's unable to saturate a 10Gb link. On the other nginx uses proper IO multiplexing (and TCP)
and is much more efficient, so it can easily saturate the link. By the way, this is why astute limits
the number of the nodes being provisioned concurrently [1].

[1] https://github.com/stackforge/fuel-astute/blob/master/lib/astute/config.rb#L81