[ELDK] ATA over Ethernet (AoE) Root Partition?

[Jerry Van Baren]

Jason Hanna wrote:
>>>> Don't see any examples in the U-boot documentation referring to AoE, however.
>>> In U-Boot? There is no AoE support in U-Boot, yet. But patches are
>>> welcome :-)
>>>
> 
> Hi Wolfgang,
> 
> Actually doesn't take much at all. Support for AoE is in the kernel so
> it seems no modifications are not necessary for U-Boot.
> 
> I think there is probably a better (faster) way to start the system,
> but with ATA_OVER_ETH compiled into my kernel - all I need to do is
> set root=/dev/etherd/eX.XpX and rootwait in my kernel command line and
> the system will wait until my AoE device is discovered.
> 
> I'm up and running! Kilauea board with a cross-compiled GNU/Linux
> 2.6.26-5 kernel root-mounting its drive via ATA over Ethernet. Debian
> Lenny installed and OpenJDK 6 running and compiling Java!
> 
> Thanks for all your help. I'll keep everyone posted as I find time to
> do some benchmarking.
> 
> Regards,
> -jmh

Pretty cool.

"I've always used my ignorance as a weapon. I don't know why things 
can't be done. Engineers spend a lot of time telling us why things can't 
be done. Sometimes they're right. But sometimes they're not."
  - Garry Hoyt

FWIIW, there are some limitations as noted:
* Since u-boot doesn't know how to AoE, your kernel has to be local or 
use TFTP - not a big drawback.  As you noted, AoE is fairly simple 
(disclaimer: I have not looked at it) so we could add AoE to u-boot and 
boot off a remote HD without a TFTP-enabled host.  That would be 
interesting and potentially useful.

* One of the BIG advantages for NFS is that it is a shared disk 
resource.  This is VERY handy during development because you can mess 
with the file system directly on the host.  On the target, you can 
read/write files to transfer from/to the host.  On the host you can do 
all sorts of useful stuff to the file system you are running on the 
target with or without the target being on-line.

* Since AoE is a literal ATA emulation over ethernet, only one host can 
mount a AoE drive at a time (unlike NFS which knows how to share).

Thanks for the experiment and update,
gvb