🚀 go-pugleaf

Mike Rothenberg wrote:
> 
> Does anyone know of a device (Switch, MUX, etc.) that would allow
> two different Unix systems to share the same SCSI tape drive?  I
> don't want to have to buy 2 expensive tape drives, and I don't
> want to use NFS.
Can't you just put the two boxes on the same bus? With good SCSI
implementations, is should work... I did it between a PC and a VAX
once and it worked perfectly. Not when I accessed the tape concurrently,
obviously ;)

Ralf-Peter
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Ralf-Peter Rohbeck                                     rrohbeck@qntm.com
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In article <3189F476.744C@qntm.com>, Ralf-Peter Rohbeck <rrohbeck@qntm.com> wrote:
| Can't you just put the two boxes on the same bus? With good SCSI
| implementations, is should work... I did it between a PC and a VAX
| once and it worked perfectly. 

You need to make sure the two hosts don't try to mount each others'
hard disks.  The easiest way to do this is to one SCSI adapter in 
each host for the shared devices (tape drives, CDROMs, scanners), 
and a separate adapter for host-specific devices (HDDs).

---
chris

Ralf-Peter Rohbeck wrote:
> 
> Mike Rothenberg wrote:
> >
> > Does anyone know of a device (Switch, MUX, etc.) that would allow
> > two different Unix systems to share the same SCSI tape drive?  I
> > don't want to have to buy 2 expensive tape drives, and I don't
> > want to use NFS.

> Can't you just put the two boxes on the same bus? With good SCSI
> implementations, is should work... I did it between a PC and a VAX
> once and it worked perfectly. Not when I accessed the tape concurrently,
> obviously ;)
> 

 You can share SCSI-tape drives on the same bus if:

  - The drivers support RESERVE/RELEASE SCSI-cmd's. This locks a drive for on
    system, the other gets BUSY status until the owning system sends a RELEASE
    cmd.
  - The controllers on both end don't crash if they are selected by the opposite
    host or if the drivers are configured not to attempt it.
  - Good grounding of all hardware involved is essential.
  - Stay within SCSI length limits.
  - Start with most robust speed settings for SCSI (5 Mb/s, a-sync). If this works
    reliably, try sync. 5 Mb first and perhaps 10 Mb later. If sync. mode doesn't
    improve throughput, stick to a-syn.

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Ralf-Peter Rohbeck <rrohbeck@qntm.com> wrote:

>Can't you just put the two boxes on the same bus? With good SCSI
>implementations, is should work... I did it between a PC and a VAX
>once and it worked perfectly. Not when I accessed the tape concurrently,
>obviously ;)
>

One thing you have to do with this approach is to change the SCSI 
initiator ID on the SCSI host adapter of one of your systems.  Funny 
things happen when both host adapters claim the same ID (default 7).
-- 
Carl Appellof
not speaking for
Digital Equipment Corporation

Assuming the two Unix systems are networked, whats wrong with rtc (remote tape
controller)?

jonese@twdl03.a1.nt.gov.au wrote:

>Assuming the two Unix systems are networked, whats wrong with rtc(remote tape controller)?

To my opinion, RTC is not available with Solaris 2.x.

Do you know a "standard way" to "share" peripherals, like DLT drives,
via an ethernet network ?

I mean other ways than "rsh" !

Please reply by mail at : Stephane.Cottin@der.edfgdf.fr

In article <4mou40$a42@pellew.ntu.edu.au>, jonese@twdl03.a1.nt.gov.au wrote:
| Assuming the two Unix systems are networked, whats wrong with rtc (remote tape
| controller)?

With some drives and some networks, the available bandwidth isn't 
enough to keep the tape streaming, and the drive has to keep stopping 
and backing up.  This can greatly increase both backup time and wear 
to the tape and drive.

---
chris