[9fans] Keeping a Plan9 domain's time consistent

[9fans] Keeping a Plan9 domain's time consistent

[Lucio]

According to G. David Butler:
> 
> I've started thinking about how to keep time consistent
> in a Plan9 system.  This is one problem that is common
> with most distributed systems.
> 
You bet!  I keep having to rewind the clock on my file server because 
it foolishly believes it is running on sensible hardware :-(

> We could use timed between the file servers and increase
> the frequency of the cpu/terminal systems syncing their
> time using the existing stat of /.  This would keep the
> overhead of the timed protocol down.
> 
I run a silly combination of NTP and timed amongst some six hosts, and 
the result seem surprisingly good (this on NetBSD - the NT boxes aren't 
yet synced, although SAMBA would take care of that, I believe).  I'd 
love to do better though, and the Plan 9 docs hint that it may be 
possible, where they suggest that Bell Labs use an external source for 
their time.

> Or we could run ntp on the auth server and slave all the
> other systems from that.
> 
The NTP docs argue that timed and ntp should not run on the same host, 
but I could find no good reason, nor a practical alternative.  I'd love 
this issue to be clarified.

++L

[9fans] Keeping a Plan9 domain's time consistent

[Nigel]

I have an sntp client in my fs which uses UDP only. The mods
to be able to originate IP from the fs are small, so long as
the time server is on the local segment of ether0!

I use forsyth's timed to distribute time from the auth server, and
a Galleon ARC Rugby clock receiver attached via a serial port
to set the time in the auth server.

[9fans] Keeping a Plan9 domain's time consistent

[Juhani]

On Sat, 19 Dec 1998, Lucio de Re wrote:
> 
> The NTP docs argue that timed and ntp should not run on the same host, 

Don't believe everything you read :-)

> but I could find no good reason, nor a practical alternative.  I'd love 
> this issue to be clarified.

I have run them on the same host without problems. The ntpd is allowed 
to change the system time and it is synced both with external source and 
local clock. The timed is used only for time delivery because it is fixed
to local system and it is modified not to change the system time. All
other hosts are just fixed ntp or timed clients which get their time from
this particular server. 


	jf

[9fans] Keeping a Plan9 domain's time consistent

[Bengt]

In article <199812181728.LAA22026@ns.dbSystems.com>, 9fans@cse.psu.edu wrote:

> Hello 9fans!
> 
> I've started thinking about how to keep time consistent
> in a Plan9 system.  This is one problem that is common
> with most distributed systems.

My favorite books on the subject (distributed systems) always suggest that
one should avoid a centralised solution. This is due to the lack of
scalability of such a solution. However, with a Plan9 system the auth
server is a centralised already, no?

> We could use timed between the file servers and increase
> the frequency of the cpu/terminal systems syncing their
> time using the existing stat of /.  This would keep the
> overhead of the timed protocol down.

(I will try to understand this and perhaps comment if I manage)

> Or we could run ntp on the auth server and slave all the
> other systems from that.

How about mount:ing /dev/time from the auth server? Would that save the
other systems from running ntp?
 
> The only requirement is that the protocol be il or udp
> based so we don't have to add tcp to the file servers.
> 
> Any thoughts?
> 

Would a DNS like system make sense? File servers sync with the auth
server. Cpu servers sync with a file server (the least recently used).
Terminals sync with cpu servers (also the least recently used). I hope
this is a none centralised suggestion, and that it might scale.

[9fans] Keeping a Plan9 domain's time consistent

[G.David]

Hello 9fans!

I've started thinking about how to keep time consistent
in a Plan9 system.  This is one problem that is common
with most distributed systems.

We could use timed between the file servers and increase
the frequency of the cpu/terminal systems syncing their
time using the existing stat of /.  This would keep the
overhead of the timed protocol down.

Or we could run ntp on the auth server and slave all the
other systems from that.

The only requirement is that the protocol be il or udp
based so we don't have to add tcp to the file servers.

Any thoughts?

David Butler
gdb@dbSystems.com