ThinkC Nested Volume Manager DA in Megamax C

[JDW]

I've known about this Nested Volume Manager article (by Mike Schuster of Adobe, April 1986) since 2007. I've always thought it was a neat concept, which I will summarize thusly:

Format a HDD like the Apple HD20 (serial interface) and then use the special Desk Accessory (DA) and driver (mentioned in the article) to format the volume HFS, but then make partitions in HFS or MFS, if you like.​

A large amount of source code is mentioned in the article, and in the closing "A Few Comments" section, it says the compiled DA and source code were distributed on "disk #7 from MacTutor's mail order store." That source code and compiled app and DA are found on the MacTech CD-ROM on Macintosh Garden. I downloaded that CD and extracted the relevant content today, making that a separate SIT file for convenient download here:

https://macintoshgarden.org/apps/mactech-vol-1-12

@Crutch started a discussion about this on the MLA here in December 2020, but nothing ever came of it.

I installed the DA into the System file of System 2.0, 2.1, 3.0 & 3.1 and tested. These are all System files that would have been accessible to Mike Schuster at the time he wrote that article. Sadly, when I install the DA and then launch the Nest Manager app, it throws an error dialog:

Could be that a real HD20 must be attached to a real Mac for it to work. Not sure. I only tested it in Mini vMac so far.

I am not a C programmer and really don't have the ability to take a deeper dive into the code to see what might be triggering that error dialog, but I think it would be fabulous if we really could format an HD20 such that we could have MFS partitions alongside HFS partitions. That's important because folders on MFS volumes are fake illusions. MFS also limits the volume size to 20MB.

---

By the way, I did a little write-up below, for those of you wanting to know how to format a 20MB HD20 drive image as MFS, for use on a FloppyEMU (or you could even format a real HD20 this way):

https://tinkerdifferent.com/threads/warpse-25-mhz-68hc000-based-accelerator-for-mac-se.253/page-36#post-33083

 

[eric]

-43 is File not found error - and reading the article you linked it says:
"Use Apple's ResEdit application to copy the .Nest DRVR resource from the Nest suitcase and paste into your system folder."

.Nest is driver - though regardless it'll be anyones guess if minivmac would even support this (as it takes things over with it's own driver)

Note to lookup errors on a modern machine you can goto https://www.osstatus.com/search/results?platform=all&framework=CarbonCore&search=-43 - though you'd have to be a developer to understand the shorthand that fnf means file not found.

 

[JDW]

-43 is File not found error - and reading the article you linked it says:
"Use Apple's ResEdit application to copy the .Nest DRVR resource from the Nest suitcase and paste into your system folder."
.Nest is driver - though regardless it'll be anyones guess if minivmac would even support this (as it takes things over with it's own driver)

Eric, thank you. Here are some screenshots...

App and Driver "suitcase" icons:

"Nest" suitcase opened in ResEdit:

Copying ONLY the DRVR from the Nest suitcase into a given System file is easy. But I'm curious what leaving out the other 5 resources will do.

 

[JDW]

Instead of working on WarpSE on my lunch break today, I took my standard 4.5km brisk walk. That usually gets my aging brain working a bit better.

I believe what the documentation must be saying is to copy only the DRVR resource from the NEST suitcase (via ResEdit) into the System file, but then put the NEST suitcase into the System file via Font DA Mover because it is a DA. I'm going to test that shortly, but I believe that's the goal here.

Thankfully, the Resource IDs are not the same, making a copy/paste easier to do (below at right are existing DRVR IDs for System file 3.0:

UPDATE:
Seems that my guess was correct. When launching the app or the DA, it shows me this dialog box:

I then mounted a 20MB HFS volume and clicked the Drive button shown in the above screenshot. That in turn shows me this:

Very exciting! Now for some testing...

I tried making a 10MB MFS partition like so:

But that throws the following error dialog about a locked disk and not being able to create the Desktop file as a result:

But, when clicking OK, it then shows me this:

Of course, that wasn't what I was expecting. When creating a "partition" you want a new drive icon to appear, not what looks to be a disk image! Hmmm...

Double-clicking that file shows the following dialog box, which implies it is already "mounted" as per the existence of an "Unmount" button, which has me quite confused because again, there's no new drive icon appearing on the desktop. You know, the a drive you can double-click to open a window, into which you can copy files.

Clicking the Unmount button merely takes me back to the desktop and shows me exactly what my screenshot above shows (the single "10MB-MFS" disk image icon sitting inside the "20MB-Test" drive window.

Clearly, I need to test this on other versions of the System file to see if System file version matters. But with System 3.0, it's clearly not working in a way that my feeble brain can understand.

UPDATE:
I figured it out. You have to put a System Folder on your hard disk and then boot from your hard disk, and then you must launch the nest App or DA, then choose your partition file, then Mount it. After that, it will appear as a separate drive icon like this:

Obviously, it would be best to work like modern partitions do. You know, all partitions are mounted automatically when you boot and there are no visible partition files. But when this software was created it was early days, so we can't complain about that.

Simply put, you can now have MFS "partitions" on an HFS volume.

How do I really know that 10MB-MFS drive is truly MFS, you ask? It lacks the magic dot...

Closeup of the HFS-formatted 20MB-Test volume's window, showing the dot:

Closeup of the MFS-formatted 10MB drive partition, which lacks the dot:

BAD NEWS​

I tested with System file v.3.0 and v.3.2 (using their respective Finder files). I made MFS volumes of 400K, 800K and 10MB sizes. I also made HFS volumes too. I couldn't copy any files at all to HFS volumes I made. And while I could copy files to the MFS volumes, when I rebooted, I couldn't delete or add files to the MFS volume. Also, trying to launch apps from the MFS volume results in a crash.

Neat concept, but not usable. If it could be made usable, well... Then it becomes something very interesting!

 

[Mu0n]

TIL that HFS volumes have an extra dot. (won't show up in System 7.5.3, but still does in 6.0.8)

 

[JDW]

TIL that HFS volumes have an extra dot. (won't show up in System 7.5.3, but still does in 6.0.8)

The dot also doesn't appear in the windows of HFS volumes while booted into very old System Software, such as System file version 2.0, which is not HFS aware.