Filesystem spanning?

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commodorejohn
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Filesystem spanning?

Post by commodorejohn » Fri Mar 20, 2020 12:03 pm

So I'm getting back into dabbling with VMS, what with all the talk surrounding the end of the hobbyist program. Got my final PAK, got 8.4 set up on an Alpha workstation I got as a rescue, got the basics configured...but now I'm wracking my brain trying to remember how to set up a spanned filesystem, which I swear I had going on my VAXStation last time I was puttering around with this.

Basically, I really would like to have the system treating the two hard disks as one uniform storage space and spanning files across them transparently, since the only compatible disks I have on hand are in the 1-2 GB range and I'd like to get some more software installed...only problem is, when I went to look at the documentation for volume sets, one of the first things it says is *not* to include the system disk in a volume set. I swear I had this set up on my VAXStation, but it's been some years since I was last digging into this, and I never was super familiar with it...*is* there a way to do this?


snadow
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Re: Filesystem spanning?

Post by snadow » Mon Mar 23, 2020 5:09 pm

I'm inclined to agree with the documentation that says don't turn your system disk into a bound volume set - and I doubt it would be possible to do it anyway.

Another technique that might achieve something similar to what you're seeking - though I also wouldn't recommend it - is to define a logical name that implements a search list of two disks: Your system disk, followed by a secondary data disk. Then use that logical name whenever you want to access a file that is on one of those disks. It's not for the faint of heart and you'll have to be careful with corresponding directory structures and be prepared to properly handle situations where the same filename exists on both disks, etc. I did implement such a beast a very long time ago in a mixed-version VAXcluster so that the newly-added server (at the higher version of VMS) could still have its own system disk, yet be able to access many shared directories and command files on the existing system disk (at the lower version of VMS.) It worked. But it wasn't pretty! And we made sure to only keep that configuration for a short while until we could make everything consistent across all the servers. (As I think back - I'm not 100% certain - but it might have been SYS$SYSDEVICE that I redefined as a search list. Be careful!)

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