wayne@dsndata.uucp (Wayne Schlitt) (12/06/89)
[note 1: i have added comp.windows.x to the newsgroups lines. i
think both groups would be interested in this topic]
[note 2: i realize that although the subject line says "X-term v.
PCs..." that most of the actual discussion has been on the pros and
cons of MIS departments. for the most part, this is irrelevant
to me, the company i work at, and our customers. ]
i am very interest in subject of X terminals vs. PC's running X vs.
diskless workstations vs. disk based workstations and when to use each
of these systems.
over the next year or so we are going to be replacing most of the
computers on our (nonstandard and slow) lan with something that will
run X. we are also going to have to start selling systems that run X
and our customers are very interested in low-cost systems that have
reasonably high performance. (i.e. even if system XYZ has great bang
for the bug and super performance, they wont want it if it costs over
$20k per seat. if it gives even "ok" performance for around $3-5k per
seat, they will jump at it.)
a little background might help. we sell a cad package that's main
claim to fame is that we have large processing and picture creation
programs that let our customer put a little bit of information in and
get out finished cad drawings. most of our customers use small lan's
(less than 5 seats), but networking is very important to them. our
customers will typically spend equal amounts of time in the cpu & disk
bound programs and our graphics package, although any given person may
spend most of his/her time in only on only one of these two programs.
what i have been thinking about recommending using is a "large" main
cpu/disk server that will run the cpu/disk bound programs. the
graphics package i am not really sure where they should run. would X
terminals give good enough graphics performance, or would it require a
workstation of some sort? the second question is which is better, x
terminals or pc's running X and discless vs disc based workstations?
as i see it, each system has advantages and disadvantages.
X terminals:
Advantages:
* "cheap", possibly the least expensive of all.
* everything you need to run X is already put together for you.
you dont have to add lan cards, or install operating systems
* all of the advantages of using a central cpu server:
* economy of scale. it is usually cheaper to by one 4meg
board than 4 1meg boards, and one 300 meg disc than 5 60meg
disc's.
* one point system maintenance. only one system to back up.
only one system to upgrade with a new operating system. if
your central system is a multiprocessor, you can add a cpu and
everyone benefits. if you add more memory, everyone benefits
* shared resources. only one copy of the operating system,
utilities, and application programs on disc. only one copy of
the operating system taking up memory (as opposed to having to
buy memory for each workstation to run an operating system).
application programs that are being used by more than one
person are shared in memory rather than being duplicated on
each workstation. since X programs tend to be large, this is
more important than if you are running different copies of "vi".
* one of the advantages of decentralized computing:
* you can add "graphics power" by adding additional X terminals
Disadvantages:
* can you upgrade the terminal to use X11R4 (or whatever). does
this make a difference?
* everything that goes to the screen must go over the lan. highly
graphically oriented programs may use up a lot of the lan's
bandwidth.
* all of the disadvantages of using a central cpu server:
* economy of location. a central computer may be faster and
cheaper, but it cost time and resources to transmit
information to and from it. the central computer may be able
to figure out what to draw in half the time, but it make take
longer to get that information to the screen.
* response time may be inconsistent. if lots of people are
trying to do things on the central server, it will take longer
to get things done.
* if the main system goes down, everyone stops working.
personally, i dont really agree with this argument. if the
lan goes down, everyone stops working too. and the bigger/more
complicated you make each workstation, the more likely it is
to go down. you may end up with less _total_ downtime by
using a central server. i generally dont consider this to be
a very important consideration.
* you can't add cpu power without upgrading the "entire system".
that is, if you use distributed computing, you and add cpu
power by just adding another workstation and you can give one
person a much faster workstation and give the old workstation
to someone else. of course, there is still the problem of
what to do when you need to upgrade your lan, so in a sense
you always have an "entire system" that may need upgrading...
PC's running X windows
Advantages:
* "cheap", possibly cheaper than X terminals...?
* you can run other things besides X, such as dos programs.
* people may already have PC's. (this is not the case for us)
* upgrades are definitely possible. both with newer/faster
hardware and with newer software.
* for X programs that run on the central server, all of the
advantages of centralized computing.
* for programs that run under dos, all the advantages of
decentralized computing. assuming of course that you can use
the lan for dos. i am not sure how many dos network will work
on the same lan as unix. pc-nfs may be a solution.
Disadvantages:
* you have to put things together. making sure the X software
works with the graphics card, lan card and the server. this may
be a _major_ problem, depending on how much you know about dos,
dos related hardware and how many different combinations you
have.
* like the X terminal, everything that goes to the screen must go
over the lan. highly graphically oriented programs may use up a
lot of the lan's bandwidth.
* for X programs that run on the central server, all of the
disadvantages of centralized computing.
* for programs that run under dos, all of the disadvantages of
decentralized computing.
diskless workstations
Advantages:
* cheaper than disk based workstations.
* you can run other things besides X, such as unix programs.
* upgrades are almost always possible. both with newer/faster
hardware and with newer software.
* X programs that do a lot of screen i/o can be run locally. but
if you run X programs that use a lot of disc i/o locally, you
can bog down the network. if your program uses both disk i/o
and graphics, it may be hard to tell where to run them. (our
programs usually do one or the other, but not both)
* for X programs that run on the central server, all of the
advantages of centralized computing.
* for programs that run run locally, some the advantages of
decentralized computing. the main difference is that disc i/o
must still go through the central server.
Disadvantages:
* swap space for each workstation must be reserved on the main
server.
* the absolute minimum amount of memory need on a workstation is
probably around 3 meg, for the operating system and x server.
this doesnt include the mrmory for actually doing real work.
you will probably need a minimum of 1 meg for each x program
that you plan to run, including xterms and such. our programs
are probably going to require about 3-5meg.
basically, you are looking at 8-16meg of memory for a diskless
workstation, a lot of it could have been shared by multiple
users if the programs (and operating system) were run on the
main server.
disk based workstations
Advantages:
* this configuration will probably give you the most consistent
response time.
* you can run other things besides X, such as unix programs.
* upgrades are almost always possible. both with newer/faster
hardware and with newer software.
* X programs that do a lot of screen i/o can be run locally.
* programs that need to do disc i/o that arent to shared files can
do the disk i/o locally.
* for X programs that run on the central server, all of the
advantages of centralized computing.
* for programs that run run locally, most the advantages of
decentralized computing.
Disadvantages:
* on the surface, this appears to be the most expensive option.
* memory requirements are going to be about the same as a discless
workstation, and again, a lot of this memory could have been
shared if things were run on the main server.
please let me know of any advantages or disadvantages that i have
forgotten. also please point out anything you disagree with.
i realize that many of pros/cons are really two sides of the same
coin. arguments in the form of "well, the pro's outweigh the cons, so
the cons are irrelevant" probably wont help much. i am much more
interested in _why_ you think the pro's outweigh the cons.
anyway, my _real_ concerns with each option are:
X terminals:
* are they really the cheapest option?
* are they really fast enough to do useful work?
* am i going to be stuck two years from now when X11R6 comes out and
my X terminal is X11R3 based?
pc's running X:
* compatibility between all of the parts is a real concern. has
anyone actually put together a good reliable configuration? if
you have, please let me know.
* will pc-nfs really work well to network the dos programs? does
anyone know where i can get a copy of pc-nfs?
diskless workstations:
* will they bog down the network so much that to make them useless?
* are they really going to be any cheaper than disc based
workstations
disk based workstations:
* could this really be the cheapest system when everything is
considered?
please mail or post your replies. i will try to summarize the mail
responses that i get.
thanks much for any help...
-waynelamaster@ames.arc.nasa.gov (Hugh LaMaster) (12/09/89)
In article <WAYNE.89Dec6092647@dsndata.uucp> wayne@dsndata.uucp (Wayne Schlitt) writes: >a little background might help. we sell a cad package that's main >claim to fame is that we have large processing and picture creation >programs that let our customer put a little bit of information in and Your customers will decide which way they want to go. Objectively speaking, it may not be the most cost effective way to go for them. The important thing is for you to offer an X interface on the system of their choice. (P.S. We use Ultrix DEC/VAX, SGI 4D Irix, SunOS Sun-3's and Sun-4's, Convex C2xx, and Cray UniCos here :-) >what i have been thinking about recommending using is a "large" main There is no single answer. You will have customers that use all of these arrangements. > utilities, and application programs on disc. only one copy of > application programs that are being used by more than one > person are shared in memory rather than being duplicated on This brings up the question of how you will handle licensing. Frame Technologies and Sun both have distributed license server arrangements so that the number of active programs is what you pay for. This type of arrangement is now a necessity for third party software like yours. > Disadvantages: > > * can you upgrade the terminal to use X11R4 (or whatever). does > this make a difference? If you buy the right type of system, you can. This is a requirement. We have a number of NCD X terminals here (B&W) and they are downloaded from a SunOS host. I would recommend against buying a system with everything in ROM. > * everything that goes to the screen must go over the lan. highly > graphically oriented programs may use up a lot of the lan's > bandwidth. This is not an issue. The amount of LAN traffic is always *less* than what you would have if you had individual workstations, believe me. NFS is much more consumptive of LAN bandwidth. Diskless machines are a real problem. We don't have any completely diskless machines in this facility. >PC's running X windows > * for programs that run under dos, all of the disadvantages of > decentralized computing. Exactly. This is a very expensive solution if you figure the cost of the time required to support it. Also, what about resolution? IMHO, you need at least 1024x1024 resolution and, can you get that, and at reasonable cost, in the PC based solution? But, some of your customers will want to do it, so you might as well be ready. >diskless workstations > * swap space for each workstation must be reserved on the main > server. In my experience, these always end up as workstations with local tmp and swap, described below, before long, because of excess network traffic and because it is wasteful of the server CPU, which will also be a bottleneck. >disk based workstations >X terminals: > * are they really the cheapest option? Color, or B&W? B&W are cheap. If you are going to color, you might as well buy a color workstation with a local swap/system disk. B&W X terminals are a *very* cost effective approach. > * are they really fast enough to do useful work? Yes. But don't forget to put the MIPS back in the central server! I recommend at least 1 VAX equivalent (VUPS, SPECmark, whatever) per X user. Just a Sun-3/50, really. But, if you have 16 users, that is a Sun-4/490 or SGI 4D/210 or DEC 5810 or whatever, roughly speaking. > * am i going to be stuck two years from now when X11R6 comes out and > my X terminal is X11R3 based? No. Not if you buy the right kind. >pc's running X: Not recommended IMHO. >diskless workstations: > * will they bog down the network so much that to make them useless? Yes. >disk based workstations: > * could this really be the cheapest system when everything is > considered? For CAD work, still a good bet. With individual workstations, you get "fair share scheduling" automatically. Use local system/swap, plus a centrally administered user-file system server with backups, etc. >please mail or post your replies. i will try to summarize the mail >responses that i get. You need a better email address to reply to! Hugh LaMaster, m/s 233-9, UUCP ames!lamaster NASA Ames Research Center ARPA lamaster@ames.arc.nasa.gov Moffett Field, CA 94035 Phone: (415)694-6117