Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!steinmetz!trub!perley
From: perley@trub.steinmetz (Donald P Perley)
Newsgroups: comp.sys.amiga
Subject: Re: Diskless nodes (was Re: AM(iga un)IX)
Message-ID: <13425@steinmetz.ge.com>
Date: 24 Mar 89 18:47:34 GMT
References: <72@snll-arpagw.UUCP> <6330@cbmvax.UUCP> <74@snll-arpagw.UUCP> <2421@sbcs.sunysb.edu> <13392@steinmetz.ge.com> <95626@sun.Eng.Sun.COM>
Sender: news@steinmetz.ge.com
Reply-To: perley@trub.steinmetz.ge.com (Donald P Perley)
Organization: GE Corp. R & D, Schenectady, NY
Lines: 49

In article <95626@sun.Eng.Sun.COM> cmcmanis@sun.UUCP (Chuck McManis) writes:
>In article <13392@steinmetz.ge.com> (Donald P Perley) writes:
>>I am not all that hot on diskless nodes myself.  NFS is great, being able
>>to access files all over the place, but remember that you are limited to
>>a total of about 1.2 mbyte/sec.  When you start splitting that among
>>a large number of stations, it would be nice to at least have memory
>>paging on a local disk.
>
>A couple of points about diskless nodes :
>
>	1) Diskless Amigas are 98% the speed of diskfull Amigas because
>	   once they are running something they don't swap. Loading and
>	   directory scanning is about the same as a non-DMA harddrive. 

I was refering to all the brew-ha-ha about Commodore needing to supply 
their own ethernet card to have a legitimate unix workstation, and be
able to boot diskless.   Doesn't AMIX have paging?  

>
>	2) The ethernet has never been the bottleneck for diskless nodes.
>	   The order link strength is generally Server-CPU, Server-Disk Speed,
>	   Ethernet. At Sun we keep improving the Server's CPU and Disk Speed
>	   and have yet to get it to the point where either the server or
>	   the client was waiting to shove bits over the wire.


Each of the resources (server-cpu, server-disk, ethernet) are a shared
resource.  We probably have close to 500 diskless nodes here, and
dozens of servers. If all of a servers clients are clamouring for
packets at the same time, things can get kind of bogged down. 

A resource is easier to share if only one person wants it at a time.

The thing about your paging file is that your machine is the only one that
needs it, so there is no need to use a shared resource to handle it.
(unless the per megabyte cost is a lot less on the server)

>The other point you missed (and don't feel bad, most people do) is that
>ethernet is not "split" among the various diskless nodes, it is "given"
>to them. Thus whenever you need it, you get _all_ 1.2 MBytes/Sec of bandwidth
>and don't have to share with anyone. No one makes a disk drive for the 
>Amiga yet that can pump out 1.2 Mbytes a second. (Yes they come close,
>but still they aren't there yet.)

Maybe I was mistaken about the nature of ethernet.  I thought you only
get it all if no one else is asking. If a server tries to send a packet
can't it get a collision and have to retry? 

-don perley