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Conference noted::hackers

Title:	Hackers

Moderator:	XDELTA::HOFFMAN

Created:	Sun Jan 31 1988
Last Modified:	Tue May 27 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1838
Total number of notes:	13578

1835.0. "FYI - an interesting PC to OVMS connection system" by EVMS::EVERHART () Mon Apr 14 1997 13:29

    A rather interesting hack has surfaced on the net. W. Moeller
    has placed the files
    
    ndfp0530.README and ndfp0530.zip on
     ftp://gwdw04.gwdg.de/vms/
    (a VMS machine)
    
    These comprise a package that allows you to use a cheap, old PC
    as a cheap disk or file server from OVMS. That is, it can take
    tapes or disks attached to the PC and make them look like they're
    locally attached to the VMS box, or allow access to PC files as
    though local to VMS. He's using it as a way to add cheap disks
    to his home VMS systems; the package comes with sources.
    
    I have a copy of the files here for any who prefer not getting their
    own, but where a VMS box is too small or restricted (e.g., a VS2000)
    to hold much more storage of its own this can provide a way to
    access storage.
    
    I don't imagine there's much need for this inside of Digital, but
    for folks' home systems it can be quite another matter. I hope to
    use it to allow vms backup to do back/phys of PC disks, for example.
    
    Glenn Everhart

T.R	Title	User	Personal Name	Date	Lines
1835.1		AUSS::GARSON	DECcharity Program Office	`Mon Apr 14 1997 22:15`	5
	re .0 Interesting hack. In general terms, how does it work? For example, at what level does it present the remote disks to VMS? What network protocol is it using?
1835.2	it gives real remote devices	EVMS::EVERHART		`Tue Apr 15 1997 12:52`	40
	The hack is using a program on the pc end (in turbo pascal, he uses v6) to talk with an ethernet driver using one of the common pc packet drivers (public domain, available for most boards and using a common interface) to talk to the ethernet. It uses his own ethernet protocol, talking to the ethernet driver on vms. Remote disks are done at device level...they look exactly like local disks, using something derived from my virtual disk code. Remote tape is also exactly like local as far as the rest of VMS is concerned...it transports logical I/O and leaves everything else purely at the VMS end. All the PC sees is a device or partition or file or whatnot. The protocol lets him transport serial devices also...presumably a printer or the like could be made to look local too. The remote drivers over DECnet after all do all their communications to unpriv'd servers (well,the servers can do logical i/o but that's it) from user mode pieces, using a little fiddling to make them talk to local drivers. The drivers just need to ensure they get the bits to and from the user. There are tcp/ip remote disk & tape available free also, but W. hasn't been using those yet. He might, in conjunction with having his devices on NT. As it is, he's using a slow cheap IDE disk as extra VMS storage with the thing. I/O on the PC end is by the way synchronous. It doesn't attempt to have several things going at once; this is the same as remote disk/tape over decnet. Needless to say, while you could have several systems accessing the same disk, you must ensure at the VMS end that only one gets write access, or have the disks named identically and have the vms systems all in a cluster. There's no file system integration in here, and obviously the old cheap PC isn't up to it. However, the old 8088 or 286 box you might otherwise toss, if it will talk to an ATAPI or IDE drive, can become a VMS disk/tape expansion controller with this. For those not blessed with rich uncles this can be wonderful.