Mailing List Archive: Linux-HA: Users

Another possible inter-node communication system

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hm at seneca

Mar 5, 1998, 10:55 PM

Post #1 of 4 (558 views)
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Another possible inter-node communication system

CC to the linux-ha list because IMHO this is interesting for the whole
group.

On Thu, Mar 05, 1998 at 06:08:24AM +0000, alanr [at] bell-labs wrote:
> > Hi,
> >
> > > It seems that another possibility for internode communication
> > > (keep-alive messages) would be IrDA. It might be worth mentioning in
> > > the FAQ.
> >
> > Albeit very expensive and overpowered :-)
> >
> > Ciao,
> > hm
>
> I was assuming that you would only use this if you have motherboards which have
> the IrDA drivers onboard (as do several I've seen recently). Then it's only a

Ah, now I get the picture. This leaves two questions open (at least for
me):

- don't the IrDA ports normally take one of the onboard serial interfaces?
- what is the maximum distance for an IrDA link (and what would happen if
someone walks between the nodes, equivalent to what happens if someone
unplugs the serial cable, which leads to a network_down event for that
interface and node.)

> little money for the LED assembly. It's cheaper than an ethernet port, and it
> doesn't take up a slot (if it's on the motherboard). A shortage of slots seems

IrDA is not an alternative to an ethernet port because ethernet doesn't run
non-IP heartbeat. :-)

> to be a problem with Linux-HA. This would potentially allow more computers in

This is correct. Normal 4+4 (1 shared) PCI/ISA boards would be sufficient
for simple solutions (2 PCI storage adapter cards, 2 PCI 100TX cards for
example). There are also multi-port cards for SCSI and Ethernet out there
but I don't quite like the idea of using them for a HA solution because
these cards have a SPOF represented by the single PCI brigde chips that are
normally on them.

> an HA cluster than if you use the onboard serial ports. Of course, this
> assumes that you have a driver for the chip sets, etc.
>
> -- Alan Robertson
> alanr [at] bell-labs
>

Ciao,
hm

--
Reality is for those who can't face Science Fiction.

From Alan Robertson <alanr [at] bell-labs> Mon Mar 9 14:06:34 1998 [57]
From: Alan Robertson <alanr [at] bell-labs> (Alan Robertson <alanr [at] bell-labs>)
Date: Mon, 9 Mar 1998 15:06:34 +0100
Subject: Another possible inter-node communication system
In-Reply-To: <19980306065525.56008 [at] seneca>
Message-ID: <ML-3.3.889452394.7457.alanr [at] alanrhome>

Harald Milz wrote:
> CC to the linux-ha list because IMHO this is interesting for the whole
> group.
>
> On Thu, Mar 05, 1998 at 06:08:24AM +0000, alanr [at] bell-labs wrote:
> > > Hi,
> > >
> > > > It seems that another possibility for internode communication
> > > > (keep-alive messages) would be IrDA. It might be worth mentioning in
> > > > the FAQ.
> > >
> > > Albeit very expensive and overpowered :-)
> > >
> > > Ciao,
> > > hm
> >
> > I was assuming that you would only use this if you have motherboards
> > which have the IrDA drivers onboard (as do several I've seen recently).
> > Then it's only a
>
> Ah, now I get the picture. This leaves two questions open (at least for
> me):
>
> - don't the IrDA ports normally take one of the onboard serial interfaces?

I don't know. In my ignorance, I don't *think* so, because there doesn't seem
to be wiring for it. As usual, there could be IRQ problems, etc.

> - what is the maximum distance for an IrDA link (and what would happen if
> someone walks between the nodes, equivalent to what happens if someone
> unplugs the serial cable, which leads to a network_down event for that
> interface and node.)

My assumption is that you would cable the LEDs into close physical proximity of
each other (maybe even inside a box?). I don't know if there are cable length
restrictions. I don't claim to know for sure that this is a viable
alternative, but it seems an interesting thought.

> > to be a problem with Linux-HA. This would potentially allow more
> > computers in
>
> This is correct. Normal 4+4 (1 shared) PCI/ISA boards would be sufficient
> for simple solutions (2 PCI storage adapter cards, 2 PCI 100TX cards for
> example). There are also multi-port cards for SCSI and Ethernet out there
> but I don't quite like the idea of using them for a HA solution because
> these cards have a SPOF represented by the single PCI brigde chips that are
> normally on them.
>
> > an HA cluster than if you use the onboard serial ports. Of course, this
> > assumes that you have a driver for the chip sets, etc.

-- Alan Robertson
alanr [at] bell-labs

andy at globalauctions

Mar 9, 1998, 7:27 AM

Post #2 of 4 (531 views)
Permalink

Another possible inter-node communication system [In reply to]

On Mon, 9 Mar 1998 alanr [at] bell-labs wrote:
> > - don't the IrDA ports normally take one of the onboard serial interfaces?
>
> I don't know. In my ignorance, I don't *think* so, because there doesn't seem
> to be wiring for it. As usual, there could be IRQ problems, etc.

On the moboard I bought recently you had to sacrifice a serial port for the
IRDA port. I lets you choose your poison in the firmware
setup/configuration.

> > - what is the maximum distance for an IrDA link (and what would happen if
> > someone walks between the nodes, equivalent to what happens if someone
> > unplugs the serial cable, which leads to a network_down event for that
> > interface and node.)
>
> My assumption is that you would cable the LEDs into close physical proximity of
> each other (maybe even inside a box?). I don't know if there are cable length
> restrictions. I don't claim to know for sure that this is a viable
> alternative, but it seems an interesting thought.

If you do that, though, you have basically created the equivalent of a wired
RS-232 serial link, though you do have the advantage of optical isolation to
avoid the migration of (admitedly unusual) electrical events like lightning
strikes.

It is an interesting idea though...

-Andy

Global Auctions
http://www.globalauctions.com

From Alan Robertson <alanr [at] bell-labs> Tue Mar 10 04:40:04 1998 [59]
From: Alan Robertson <alanr [at] bell-labs> (Alan Robertson <alanr [at] bell-labs>)
Date: Tue, 10 Mar 1998 05:40:04 +0100
Subject: Another possible inter-node communication system
In-Reply-To: <Pine.LNX.3.96.980309090342.32749F-100000 [at] roadrunner>
Message-ID: <ML-3.3.889504804.7349.alanr [at] alanrhom>

> On Mon, 9 Mar 1998 alanr [at] bell-labs wrote:
> > > - don't the IrDA ports normally take one of the onboard serial
> > > interfaces?
> >
> > I don't know. In my ignorance, I don't *think* so, because there doesn't
> > seem to be wiring for it. As usual, there could be IRQ problems, etc.
>
> On the moboard I bought recently you had to sacrifice a serial port for the
> IRDA port. I lets you choose your poison in the firmware
> setup/configuration.
>
>
> > > - what is the maximum distance for an IrDA link (and what would happen
> > > if someone walks between the nodes, equivalent to what happens if
> > > someone unplugs the serial cable, which leads to a network_down event
> > > for that interface and node.)
> >
> > My assumption is that you would cable the LEDs into close physical
> > proximity of each other (maybe even inside a box?). I don't know if
> > there are cable length restrictions. I don't claim to know for sure that
> > this is a viable alternative, but it seems an interesting thought.
>
> If you do that, though, you have basically created the equivalent of a
> wired RS-232 serial link, though you do have the advantage of optical
> isolation to avoid the migration of (admitedly unusual) electrical events
> like lightning strikes.

My memory is that the IrDA spec allows for multiple devices to communicate with
each other, with some kind of address-resolution and assignment protocol. It
*seemed* to imply that multiple devices could talk to each other. Does anyone
out there know enough to know if that is what was intended. Maybe it was only
intended for two...

> It is an interesting idea though...

-- Alan Robertson
alanr [at] bell-labs

alan at lxorguk

Mar 10, 1998, 2:27 AM

Post #3 of 4 (526 views)
Permalink

Another possible inter-node communication system [In reply to]

> My memory is that the IrDA spec allows for multiple devices to communicate with
> each other, with some kind of address-resolution and assignment protocol. It
> *seemed* to imply that multiple devices could talk to each other. Does anyone
> out there know enough to know if that is what was intended. Maybe it was only
> intended for two...
>

Its intended to handle many to 1 communications. The big problem is the protocol
design is complex and many layered, that IMHO is the biggest thing that stopped
irda taking off. Dag Brattel (I hope I spelt that right) has a nearly working
Linux IRDA

rw26 at acf3

Mar 10, 1998, 9:47 AM

Post #4 of 4 (520 views)
Permalink

Another possible inter-node communication system [In reply to]

On Tue, 10 Mar 1998, Alan Cox wrote:

> > My memory is that the IrDA spec allows for multiple devices to communicate with
> > each other, with some kind of address-resolution and assignment protocol. It
> > *seemed* to imply that multiple devices could talk to each other. Does anyone
> > out there know enough to know if that is what was intended. Maybe it was only
> > intended for two...
> >
>
> Its intended to handle many to 1 communications. The big problem is the protocol
> design is complex and many layered, that IMHO is the biggest thing that stopped
> irda taking off. Dag Brattel (I hope I spelt that right) has a nearly working
> Linux IRDA
>

It's Dag Brattli, http://www.cs.uit.no/~dagb/irda/irda.html

--randy

From Alan Robertson <alanr [at] bell-labs> Wed Mar 11 04:38:21 1998 [62]
From: Alan Robertson <alanr [at] bell-labs> (Alan Robertson <alanr [at] bell-labs>)
Date: Wed, 11 Mar 1998 05:38:21 +0100
Subject: Another possible inter-node communication system
In-Reply-To: <Pine.OSF.3.95.980310114437.26322A-100000 [at] acf3>
Message-ID: <ML-3.3.889591101.7457.alanr [at] alanrhome>

Thanks for all the up-to-date references. I looked at the specs (again), and
it looks *possible* to do a keep-alive using it, perhaps even for "N" machines.
That's why I sent it out. I suspect the Linux drivers are months (a year?)
away from being able to do all we'd like for that purpose though. It looks
like one might be able use it as a sort of "poor-man's TCP". Connection setup
time could be a problem with "N" machines all vying to send trivial packets to
each other :-) It looks like the "multiplexer mode" (LM-MUX mode) might be
useful for letting each machine grab the link and query "who's there?" perhaps
without setting up N-squared individual connections.

-- Alan Robertson
alanr [at] bell-labs

> On Tue, 10 Mar 1998, Alan Cox wrote:
>
> > > My memory is that the IrDA spec allows for multiple devices to
> > > communicate with each other, with some kind of address-resolution and
> > > assignment protocol. It *seemed* to imply that multiple devices could
> > > talk to each other. Does anyone out there know enough to know if that
> > > is what was intended. Maybe it was only intended for two...
> > >
> >
> > Its intended to handle many to 1 communications. The big problem is the
> > protocol design is complex and many layered, that IMHO is the biggest
> > thing that stopped irda taking off. Dag Brattel (I hope I spelt that
> > right) has a nearly working Linux IRDA
> >
>
> It's Dag Brattli, http://www.cs.uit.no/~dagb/irda/irda.html
>
> --randy

From Alan Robertson <alanr [at] bell-labs> Wed Mar 11 05:37:37 1998 [63]
From: Alan Robertson <alanr [at] bell-labs> (Alan Robertson <alanr [at] bell-labs>)
Date: Wed, 11 Mar 1998 06:37:37 +0100
Subject: Linux-HA project structure?
Message-ID: <ML-3.3.889594657.1942.alanr [at] alanrhome>

Is there a list of who is working on what regarding Linux-HA? In other words,
is there some kind of structure (individuals, teams, committees, whatnot) to
the efforts associated with Linux-HA?

Here's all I know about (which isn't much):

Activity Participants
----------------------------
FAQ: Harald Milz

I'm willing to put this up on my (personal) web site, if there's more to it
than this, and others would be interested in having such a list on the web.

Thanks!!

-- Alan Robertson
alanr [at] bell-labs

From Alan Robertson <alanr [at] bell-labs> Thu Mar 12 02:41:12 1998 [64]
From: Alan Robertson <alanr [at] bell-labs> (Alan Robertson <alanr [at] bell-labs>)
Date: Thu, 12 Mar 1998 03:41:12 +0100
Subject: Linux-HA project structure?
In-Reply-To: <B1D4CEFC33F9D011AD4800805F0565F0053780 [at] hdi014s>
Message-ID: <ML-3.3.889670472.225.alanr [at] alanrhome>

Eric van Dijken <dijken [at] tfi>
> Hi,
>
> I'am working solo on a Linux HA project, using Linux Alpha systems.
>
> Greetings Eric.

Eric,

Is it something you can tell us about? I'm primarily interested in Alphas
also.

-- Alan Robertson
alanr [at] bell-labs

From Alan Robertson <alanr [at] bell-labs> Fri Mar 13 06:31:36 1998 [65]
From: Alan Robertson <alanr [at] bell-labs> (Alan Robertson <alanr [at] bell-labs>)
Date: Fri, 13 Mar 1998 07:31:36 +0100
Subject: Basic Linux-HA architecture
In-Reply-To: <199803120813.JAA27765 [at] hdxl29>
Message-ID: <ML-3.3.889770696.9124.alanr [at] alanrhome>

Eric vanDijken wrote:
> My goals are:
> - IP takeover
> - Application takeover
> - 99,9 % available system
>
> I'am currently working on a flowchart about what to do when.

I spent some time thinking about this this evening and would offer some
(probably obvious) thoughts.

First: In an HA-system, the heartbeat and IP takeover seem to be most
fundamental. So, it seems to me that you're starting in the right place.

Second: It seems that having Dynamic DNS would be most beneficial for such as
system, especially when one has a round-robin DNS configuration and wants to
gracefully shutdown a node for maintenance. What you want to do is:

A) Take node OOS (out of service) by:
1) inform DNS to stop delivering to this IP address
2) Tell the applications to stop accepting new clients
[.This may means telling Beowulf or whoever that it shouldn't
be considered for job scheduling]
2) wait a while for applications to naturally terminate
3) give applications the signal to shut down anyway
B) Take node offline by:
1) performing the IP takeover

This means that each node has to have an administrative IP address so you can
get into it even when someone has taken over its "real" IP address.

Now, without dynamic DNS, step A.1 can't be done realistically. But, before we
are ready to ship any product :-), it will be available, and would seem to be
good to plan to accommodate it, and allow for graceful maintenance shutdowns as
well as catastrophic ones.

Wandering into more random thoughts:
It would seem that a SYSV init-style directory structure would be helpful for
allowing various applications to "plug into" the HA architecture. For example:

Postulate a directory named /etc/ha.d, with a subdirectory named init.d. In
this script are various application scripts which get invoked whenever a node
changes it's HA status. For example, one could have a script named 020beowulf
which would be invoked as "/etc/ha.d/init.d/020beowulf online" after a node
successfully joined the cluster. When the cluster was taken out of service it
would be invoked with an "OOS" argument, and invoked with an "offline" argument
when the current machine was no longer any part of the cluster.

Such a convention would allow applications to plug into the HA architecture and
be informed of changes in the state of the world neatly and cleanly.

Similarly, one could imagine another directory named /etc/ha.d/config.d, with
scripts in it to be invoked when the cluster configuration changed (but not the
current machine). Similarly, one might imagine a script 020beowulf which was
called as "/etc/ha.d/config.d/020beowulf online alpha-1.kpn.com". It could
also be called with an OOS and offline argument as above.

You could have scripts in this directory which would carry out the flowchart
that you are designing.

Does this seem like a good way to think about it?

Does anyone else see the need for three states (rather than just two)?

-- Alan Robertson
alanr [at] bell-labs

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