Re: AoE INT13h progress

James Harper wrote:
> 
> Yep. Also, it is possible to figure out the geometry by reading the
> partition table on an already partitioned disk, which I believe the
> linux kernel does. With a combination of:
> 
> . AoE's geometry info
> . HEADS=255, SECTORS=63, CYL=(Total Blocks) / 63 / 255
> . Partition table derived
> 

Actually, you don't want to do the latter for something like AoE.  Since 
it's ATA, it really should behave as ATA BIOSes do.
> 
>>You only need
>>to turn AoE booting on and off if your AoE code is resident, but I
>> would suggest not doing that, and instead let the AoE-capable code be a
>>secondary download, so that it can be updated centrally.
> 
> The beauty of AoE is that it requires no tcp/ip stack at all, just the
> ability to send and receive Ethernet frames. No DHCP server or anything.
> My idea is that you can put a new ((E)EP)ROM/Flash on a network card and
> suddenly it becomes an AoE initiator. If you are relying on a server to
> tftp code from then you might as well just use an initramfs.
> 

... assuming you're running Linux as your target operating system (in 
which case, yes, you really might as well use initramfs.)

> The one thing in the settings that I forgot to mention is some way to
> nominate which shelf & slot to boot from. This would require 3 bytes of
> nv (2 for shelf, one for slot) storage. Most network cards have a serial
> eeprom that stores the MAC address and some other info. Maybe there is
> room in there, although (I think) Etherboot doesn't have a standard
> interface for accessing it. That leaves some spare CMOS space in the
> BIOS, which almost certainly isn't consistent between PC's. Maybe we can
> use the bytes from the existing harddisk specification...

Even if there is, for many cards there simply is no unused space, 
period.  Thus, you can't really rely on that space being available.

Hence I think you really want a central discovery server, and might as 
well use it to download the AoE stack.

	-hpa


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