On Thu, 31 Dec 1998, Johns Daniel wrote:
> [Sorry, this is not directly ON-TOPIC!]
>
> For a new proposal we are writing [has to do with disk
> farms], we need to connect two Linux PCs back-to-back
> through a SCSI interface! [Actually, one machine is
> legacy big iron and the other is a Linux PC.]
>
> Essentially, this means there will be two SCSI
> controllers on a SCSI daisy chain. Is this allowed?
> I would assume that the SCSI protocol only allows for
> a single controller on a channel?
No. This is called 'multi-initiator' and should be fine- although I can't
remember how many times I used to have to (re)fix the support for this in
the AIC driver.
If this is for disk sharing, then this works 'out of the box' (or should).
Rules:
Must-
SCSI IDs for devices (the initiator (host) is a device) may
be the same. Therefore, you need to make sure that the initiator
ID on the PC is not the same as the legacy iron.
Should-
Disable SCSI resets if you can or expect some 'startup heartburn'
whenever either side reboots.
I've definitely run the following configuration at varying points.
Linux Linux
Adaptec 2940 (ID 6) Adaptec 2940 (ID 7)
| |
| SCSI |
| disk (id 0) |
+-----------(/dev/sda1,2) |
(/dev/sda3,4)-----------+
Note that filesystem sharing is not supported. This configuration
is only for raw hardware 'sharing'- and in this particular case was
for a 'soft failover' configuration.
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