Computer responses to foreign OS on RAxx (or other) drives

[Teletech]

I have a lot of media that could have interesting bits on it, but those bits might be hard for the current host computer to parse. For instance, in the current situation I have some RA73s that could have been used with a VAX, PDP-11, (Alpha?), it gets worse with RL02 packs where it could be a PDP-8 pack, and even if it is for the correct CPU, it might not be bootable. So if I'm running a PDP-11, how would I know there is a VAX-made filesystem on the drive?
Obviously I'd love to have to avoid spinning up a pack under two (or more) CPUs and several OSes each! Any hints about the best OS and CPU to find this out?
My gut sense is using unix to dd a small portion of the disk might be the way to go.
I guess this also brings up media interchange. Would a BSD 2.11 RA73 be mountable under bsd 4.2 for instance?

 

[mcguire]

You can dump the first block of the device; from there it's usually pretty easy to tell what type of filesystem is on there.
Some OSs deal with foreign filesystems better than others. Of course any of the UNIXes will be the best at it, treating such devices as simple linear expanses of blocks. but VMS can handle this pretty well too. What I usually do is take an image of the disk/disk pack/etc on whatever system is convenient (has the required interface, etc) and then use tools on a UNIX/Linux desktop to analyze the resultant data. Then, once I've figured out what it is, I fire up the appropriate emulator under simh, boot the required OS, and access the volume natively.

About BSD FFS filesystems, it's been a long time and I don't trust my memory of it, but I'm sure I've mounted 4.2BSD filesystems under later BSDs, but I don't remember if there's any degree of compatibility between the PDP-11 FFS implementations and the VAX or other 4BSD-based implementations. Rather than asserting based on possibly incorrect memory, I'll just say that I'd bet that it'd work.

-Dave