Multi-user DOSEMU+SSH hardware requirements

Multi-user DOSEMU+SSH hardware requirements

[Yves J.]

Hi.

I am considering using DOSEMU distributed to remote users that are accessing the server from a 64kbps
frame relay connection through SSH or X.

I think this sollution would be insane, since there are 50 concurrent users at peak usage. I would need
a monster server for that, right? Or more than one.

From your experiences, how many concurrent users could be running a dosemu application in the same X or
SSH server in a P4 2Ghz 1gb of RAM, IDE disks?

There is also the itchy problem with locking. It is a Clipper application (again, dear reader)  with a
HUGE (700mb) DBF database. I don't have access to the code to port it to whatever better database
format.

Currently the database is being accessed through a samba share (yes, a 700mb DBF accessed from 64kbps
shared by at least 10 users). Can I expect good results when mounting that share in DOSEMU while native
clipper/windows clients will be using that database at the same time? In other words, will DOSEMU lock
smbfs files the right way? - I can't make DOSEMU access the database directly (without samba) since
that would screw locks etc etc.

Even if locks went fine, I believe it would demand hardware investments. Some suggest that we should
use a windows terminal server running the native application. No doubt it would be much easier.

In a year or so, the application will be substituded by one that uses a RDBMS database, so we will
probably migrate to Linux at last.
-- 

Re: Multi-user DOSEMU+SSH hardware requirements

[Bart Oldeman]

On Fri, 16 Apr 2004, Yves J. wrote:

> Currently the database is being accessed through a samba share (yes, a 700mb DBF accessed from 64kbps
> shared by at least 10 users). Can I expect good results when mounting that share in DOSEMU while native
> clipper/windows clients will be using that database at the same time? In other words, will DOSEMU lock
> smbfs files the right way?

smbfs doesn't support locks. Perhaps you have better luck with cifs
(kernel 2.6.x), and samba.

Bart

Re: Multi-user DOSEMU+SSH hardware requirements

[Michael Hipp]

Bart Oldeman wrote:
> smbfs doesn't support locks. Perhaps you have better luck with cifs
> (kernel 2.6.x), and samba.

Could someone explain this?

I've also seen this in the DOSEMU documentation.

Samba has tons of locking options and I've used it to serve various 
database apps to Windows boxes.

Is there some particular way in which it doesn't have locking for DOS 
apps or is this a more general issue.

(I have a db app written in Clarion that I need to run on DOSEMU so this 
is more than a hypothetical question.)

Thanks,
Michael

Re: Multi-user DOSEMU+SSH hardware requirements

[Bart Oldeman]

On Mon, 19 Apr 2004, Michael Hipp wrote:

> Bart Oldeman wrote:
> > smbfs doesn't support locks. Perhaps you have better luck with cifs
> > (kernel 2.6.x), and samba.
>
> Samba has tons of locking options and I've used it to serve various
> database apps to Windows boxes.

that's Samba with a Windows client. Here we're talking Samba with a Linux
client which is quite different.

> Is there some particular way in which it doesn't have locking for DOS
> apps or is this a more general issue.

it is a general issue. DOSEMU emulates locking via the Linux filesystem --
and some information gets lost. If you want to solve it properly you have
to attach the "DOS locking state" to the file, record it the information
to a temporary file (easy to get stale if multiple DOSEMUs are involved
though...) or have DOSEMU talk directly to the Samba server to bypass the
Linux file systems.

This is however a non-trivial coding exercise and nobody has been bothered
to implement it so far -- I certainly won't be bothered as there is not a
lot to gain (except for being happy about the decrease in mailing list
posts about locking problems). Maybe this post will inspire others.

Or... load a DOS network client (the MS client, or mars-nwe, or....) in
DOSEMU and let it talk via the network instead of going via lredir. This
is what several posters here mentioned and will indeed be more reliable
since the Linux filesystem is bypassed, so no information is lost.

ie. (here MFS is the Mach File System -- the code that DOSEMU uses to map
Linux directories to DOS directories via lredir)

strategy via smbfs/samba:
DOS program -> DOS -> DOSEMU (MFS) --(info lost here)-> Linux --(more info
lost here)-> smbfs -> Samba -> *nix

strategy without smbfs
DOS program -> DOS -> DOSEMU (MFS) -> Samba -> *nix

strategy via MS SMB client/samba:
DOS program -> DOS -> MS SMB client -> DOSEMU (networking) -> Samba ->
*nix

note that I never tried this myself but it's based on my experience
with the DOSEMU filesystem and what others posted.

Bart