#SCSI Networking??
29 messages in this thread
Here's a SCSI question for the Guru's: I've heard that it's possible
to hook up both an Amiga and an IBM onto the same SCSI chain.
(Appearantly, all you have to do is set the controller ID # numbers
to different values.)
Would it be possible to do the same with 2 Amigas?
It would be really cool if I could hook my 4000 onto the same
SCSI chain as my old 3000. This way, I could share data between
the 2 platforms without having to setup some kind of networking
scheme.
Just think, networking without the expense . . .
Keep On Toastin'
Erik Flom
How do you come up with this stuff 🙂
Cool idea….
–Paul < Motorola Inside >
It's immensly more of a pain in the arse than it is worth. I've done
it with three Amigas, there should be no problem doing it with a PC,
too. It tended to be flaky (extra SCSI bus noise and load that,
which technically within spec, is significantly higher than most
controllers are ever used with). And you have to have only one
machine which can write to any given HD partition because otherwise
you'll scrogg the disk. Buy a network, it's worth it.
Hmmm the problem with the parallel writes could be removed with
something like parnet or sernet which would notify the other machine
of reads and writes. And one could then patch the system so that
access to the SCSI bus would first have to cleared by checking for a
file or something. It could be as easy as just patching the
SCSI.device and some parts of DOS… 🙂 … Said he with a smile on
his face!
But then again who'd set up a system like that with 125 patches, a
load of soldering, 2 or 3 parallel file access systems, 2 or 3
parallel networks, a whole load of coordination, and 3 years before
all the bugs are out?
Oh, I didn't consider the effect of buffers when both machines can write
to the same disk. I could see as to how the data could be out of sync.
Still, it might work for a 2 Toaster Workstation/Renderstation setup . .
.
I do agree it would be best ot go with a network, and I probably will go
that route.
It was just a thought . . .
Thanks,
Erik Flom
Erik,
It really doesn't have much to do with buffers, but with each machine
independently writing to the disk. That can easily put the diskmaps that
each machine keeps end up being way out of sync.
And, of course, that means disappearing files, partially
overwritten files and so forth.
Still, if it was setup with a read-only and write-only partition for each
side . . .though I'm not clear on how you'd set one CPU to be read-only
and the other write-only to the same hard drive?
Erik Flom
"…I'm not clear on how you'd set one CPU to be read-only and the other
write-only to the same hard drive?…"
It is not the cpu but the device your using that is set. The SCSIDOS
I use with my KRONOS controllers has a device setup list called
devsetup, and it is installed using a command called DEVINSTALL.
Shell 1> devinstall @devs:devsetup -quiet
In the devsetup is a line that can be set to reads only.
Here is an excerpt from devsetup, note that you can set the HOST ID # and
the write/read options.
Device CLtd.device /* Set Device */
Define Handler SCSIf.handler /* Define Handler code file name*/
Load Handler SCSIf.handler /* Load Handler code segment*/
Define Driver HardDisk.driver /* Define Driver code file name*/
Load Driver HardDisk.driver /* Load Driver code segment */
Define Driver KronosPrt.driver /* Define Driver code file name*/
Load Driver KronosPrt.driver /* Load Driver code segment */
Initialize Handler 100 /* Initialize Handler */
HandlerCode SCSIf.Handler /* Code Segment Name */
TaskName SCSI_Bus_2 /* Set Up Task Name */
TaskPriority 15 /* Handler's Task Priority */
StackSize 400 /* Stack Size */
HostAddress 7 /* Our SCSI address number */
Flags Arbitrate /* Enable Arbitration */
Flags NoDisable_IRQ /* Do Not Hold Off Interrupts */
ExitInit
Initialize Unit 1000 /* Initialize Unit */
DriverCode HardDisk.driver /* Unit driver code segment */
HandlerNumber 100 /* Uses SCSI From Above */
TaskName Unit_1000 /* Set Up Task Name */
TaskPriority 12 /* Unit's Task Priority */
StackSize 400 /* Stack Size */
AutoRetries 4 /* Number Of Auto Retries */
BufferSize 8 /* Number Of Block Buffers To Use*/
UnitAddress 0 /* Controller's SCSI Address */
Unit_LUN 0 /* Logical Unit Number / Controller */
Flags NoDisable_IRQ /* Do not Hold Of Interrupts */
Flags NoDisableBuffer /* Disable Buffering */
Flags BlockRead /* Block Reads */
Flags NoBlockWrite /* Block Writes */
Flags NoSectorSize256 /* 256 Byte Sectors */
Flags AdaptiveBuffer /* Adptive Buffering */
Flags NoWriteProtect /* NoWrite Protect */
ExitInit
Since each controller has its own devsetup file you can set any partition
or device to be WriteProtect or NoWriteProtect and give it a different ID
number. Too bad it doesn't have the ability to automatically check the
device's bitmap first when it accesses it.
Chris
Erik,
You set it in the driver. It rejects write commands. The other can be
both read and write.
Don
Erik,
IVS had some support for SCSI networking a while back, but they never
really pushed it. I would talk to them first.
//Jonathan,
\\//via AutoPilot
Erik,
I have been using just that setup with an A1000 and an A2000. It is called
SCSI-DOS and it was developed during the CLtd involvement with Amiga.
I would use the A1000 for BBS uploads to my system. Then I'd move them
to my A2000. I could access the A1000 drives with the A2000 and limit
the A1000 access to specific partitions. Only problem is that the
device bitmap is not updated after the disk is written to so when the
other Amiga access that partition after the other writes to it, it
will crash when it can't things. I usually issue the diskchange
command quite regularly, during the busy times. I miss them days.
Chris
Hmm, the whole idea is kind of interesting.
It would be real fast, if there was some way of keeping the allocation
bitmaps synchronized. . .
Thanks,
Erik Flom
Well it does work well, but they never got far enough with it to make
it bullet-proof before the company closed its doors.
What I did was give each machine its own partition with an ADOS system
on it. And made these read-only for the opposite machine. The way to
keep the allocation bitmaps synchronized is to have a Diskchange
command issued prior to any reads from a device. I guess some command
to update the bitmap in memory could be used instead, if such a
command existed. The system worked real well, but the controllers
must be capable of having their SCSI ID # changed to something other
than seven. I was able to use my SCSI printer and scanner with the
A1000, access the four partitions I had on one hard drive, the
internal Syquest device and the internal drive on my A2000. It
was(is) real fast.
Chris,
This is not directly specified to you, but you seem knowledgable
about SCSI networking, and I needed some way to break into the
thread! But is it possible to network PC SCSI with Aiga SCSI? I
have a bridgeboard and am thinking of getting a CD-ROM (also would
like to share my Syquest), Could I get a PC-SCSI controller and tie
it into the amiga SCSI chain to allow me to read the CD-ROM without
having to swap cables? Writes wouldn't come into the picture to
complicate things (unless I use the syquest but htat is not improtant
and could forego that). What would be invovled? Is it possible?
Steve,
RE: Connecting a PC SCSI controller to your Amiga bus.
Yes, I see no reason why it can't work. In fact, another member has
mentioned he is doing just what you are asking. You have to set the
SCSI controller on the PC side so its ID number is not being used by
another device on the bus. Most controllers use ID #7, if you can set
the PC SCSI controller to something other than that, and your Amiga
devices each also have an unique number to themselves than all should
work.
I'm sure someone who is now doing this very thing will jump in here
and explain his procedures for hooking up the PC SCSI controller to
the bus. Mike Schiller, is it you that is doing this?
Chris,
Thanx for the reply! At this point in time it (CD-ROM) is wishfull
thinking, have just made enough hardware purchases for the next 6 months!
But am looking down the road and the fact that it is doable will encourage
me to save my pennies!
…Steve
====>>> Motorola 68030 Inside <<<====
Steve, Steve, Steve,
Like so many others your not using EMC to it's fullest….we are the
bridgeboard experts you know.
Yes it is possible, and yes I can walk you through the set up. I also can
recommend SCSI controllers, and get you one if you decide to go that
route. Remember we carry a FULL line….I do bulid clones (ACK!!)
Give me a call….
Dave
Elite MicroComputers – Flying high on AutoPilot
Dave,
I will keep you in mind when I do this, I am pleased with EMC's
service thus far and will give ya a call when/if I get the CD-ROM.
BTW from your ads and talk here I was under the impresion that mostly
what you did was build the 486 BBs. Might not be a bad idea to make a
list of products and services and put them in the libraries here. I
really do like doing business here on Compuserve, it is so convenient!
> Remember we carry a FULL line….I do bulid clones (ACK!!)
You have my heart felt sympathy.
…Steve
====>>> Motorola 68030 Inside <<<====
Erik,
In theory…yes, it's possible.
Don
Erik, I have my A1000 and A2000 connected as you have suggested. It
works great except for one flaw. Both machines can not be allowed to
write to the same hard drive partition. I set my machines to be able
to write to their own partition. There is a Common Read Only
partition which has most of the shared software.
I don't think the problem is that the contollers try to use the SCSI Bus
at the same time thus locking it up. But seems to be that the computers
keep track of the file system and when one updates it the other doesn't
know about that update and can write over it. This can cause a large
heartburn as you see your setup being destroyed.
David A. Dette
Thanks for the feedback. It is an interesting and cheap solution to the
problems that arise when you have 2 Amigas and want to share data.
Something like this could be easily setup for a Modeler/Renderer set of
Amigas.
Thanks,
Erik Flom
It's fun to mess with. Just make sure that you have a current backup of
your drives, BEFORE you start! One last note, messing with this kind of
setup can waist a considerable amount of time.
Have Fun,
David A. Dette
Hmmm, wonder if this would work if one of the machines was a CDTV with a
SCSI board and some hard drive space or a diskette drive for the necessary
drivers.
Ron, I think you would be limited to devices actually on the SCSI Bus,
with a SCSI Address. So I don't think this would work if you wanted to
have the CDROM of your CDTV or Floppy diskette drive accessable.
Unless of course the CDROM drive of your CDTV is connected as a SCSI
device. As I have no experance with the CDTV I cannot comment on this.
David A. Dette