[K12OSN] Tossing around an idea...need some input

[John Baillie]

David Trask wrote:

>Ok...first the layout....
>
>I have 2 K12LTSP servers....both are single NIC servers since all machines
>are on the same subnet....no private subnets for terminals...everyone on
>the same network.   To simplify this I have a seperate machine that runs
>DHCP.  DCHP is turned OFF on the K12LTSP boxes.  I use the "next server"
>and "option root path" on the DHCP server to tell the terminals where to
>go to get their image (kernel).  Now...up until now I've only had one big
>K12LTSP server so all of this was easy...now I have another and would like
>to try a combination of load-balancing and/or failover.
>
>snip --->
>  
>

>Ideas.....thoughts?  Suggestions?  Perhaps a script or two?
>  
>
I have been scratching my head over this subject too.

My first thought was round robin DNS. Round robin DNS works great for 
http, ftp and even mail servers but a quick response from #LTSP informed 
me that there is no name resolution at the early stages of the LTSP 
client boot sequence.

I was wondering if the logic could be built into the os on the terminal?

For instance if you drop to a shell in SCREEN_02

and unplug the network cable you see "nfs at 192.168.0.254 not responding"

at this point we have lost control of the os because / is nfs mounted 
but there is a 1MB /tmp mounted on a ram disk and is still there.

seems like it would be possible pass an argument that says if IP X is 
not responding try IP Y

Since we have multiple ltsp servers running and / is mounted off of 
server1 whats stopping us from mounting all available
root dirs as:

/
/ server2
/ server3
/server4

and so on.

if server 1 goes down rerun the pivot_root (refer to step 9 in the 
theory of operation)


The above is for fail over.


For load ballancing

at step 7 and 8 in the theory of operation we have already loaded the 
kernel and dhclient runs.
Quote:
"A small DHCP client called* dhclient* will then be run, to make another 
query from the DHCP server. We need to do this separate user-space 
query, because we need more information than the bootrom retrieved with 
the first dhcp query."

For multiple ltsp servers it seems like we need even more information. 
Like what's the state of all our servers. Run a script that queries 
servers and builds a file. Apply logic to said file and determine what 
server dhclient will poll.

Am I barking up the wrong tree here?

John