Thank you, your detail is greatly appreciated :)
I have one other strange question ... is it possible to carve a single
physical switch into two logical switches (put a cable between ports
16/17 and modify the routing tables ... this seems like it wouldn't work
as the Unicast LID / Switch: guid rows in the respective files below
serve as keys so the single switch would be identified twice).
Not that I am aware of. When you say you have a single switch I assume you mean a switch
based on a single switch ASIC? Like a 24 or 36 port "pizza box" switch.
Yes, a 36 port Mellanox pizza box with a single crossbar ... based on
how I read these files, it looks like they key off a single GUID that
identifies the switch ... which would probably make the subnet manager
unhappy if I arbitrarily tried to mock it up being two switches somehow
The file formats seem to be:
opensm-lfts.dump (later becomes -U [file])
- Contains all discovered ports (powered on), their function (Switch vs.
Channel Adapter), their LID and some extra information. This is
essentially the physical network (if all machines are powered on) ...
the format is:
Unicast lids [0-x] of switch Lid LID# guid<GUID> ('switch description'):
<LID 0xZZZZ> <SwitchPort ZZZ> #<Channel Adapter | Switch> portguid
<GUID>: 'Descirption'
I assume this file grows with all of the Channel Adapters and switches.
Given a switch-switch connection a row would look like
0x0019 005 # Switch portguid 0x000000000000003 'MF3:switch-my:MTS3600/U1'
Yes this file grows with more nodes in the system. But the line above is not a connection but
rather a linear forwarding table entry. In general, this is saying that for the given lid
"0x0019" route out port 5 of that switch (the switch given by the "Unicast lids
[..." line. The information after '#' is more information about the node with lid=0x0019.
This is _not_ the other end of the link on port 5.
Ahhh, I see ... so this table could get quite large ... if I have 1,000
nodes in a subnet, each with a LID assigned, this table would become
quite large as each LID would be listed for each switch if I have my
forwarding thoughts in my head ... maybe I need to wander around and
steal another switch from someone ;-)
The topology of the physical connections are shown in opensm-subnet.lst.
Ahhh, but the opensm-subnet.lst is not handed to the file routing
algorithm ... this must be "derived" at runtime each run I'm guessing
and then dumped to /var/log. Very helpful! Thank you for the pointer.
You could essentially use this file to map the entire physical network,
you would end up with a graph ... but no information for how to traverse
it efficiently, does that sound right?
No this is not mapping the physical network. It is a dump of the port
forwarding which was programed into each switch by opensm.
Changing this file is what allows you to change the routing and then feed it
back into opensm.
opensm-lid-matrix.dump
- Looks like it contains the hop information ... but it's a bit more
cryptic since I have only one switch :( It should contain a list of all
switches, the LID for the switch and then hop information. The hop
information is what I'm a bit puzzled about here, as well as what port
guid information is tacked on. The format of the file is:
Switch: guid 0x000000000000x
<LID 0xZZZZ> 00 ff ff<hops for all ports> # portguid 0x0000000
That is the switch to switch hop count information. Probably not of much use
with only 1 switch.
Ugh ... I need another switch or .dump files from someone ... I haven't
found any stray .dump files out on the network, but then, Google knows
all and someone must have posted a couple somewhere to play with.
Thank you so much again Ira, I wasn't too far off and mostly it seems
I'm off in places that having only a single switch wouldn't let me see.
The semantic correction of opensm-lfts.dump was critical.
Cheers, have a wonderful weekend.
Paul Monday
Parallel Scientific, LLC
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