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From: d88-jwa@nada.kth.se (Jon W{tte)
Newsgroups: comp.sys.mac
Subject: Re: How about virtual disks APPLE ????
Message-ID: <1544@draken.nada.kth.se>
Date: 31 Aug 89 19:35:17 GMT
References: <3245@wasatch.utah.edu>
Reply-To: d88-jwa@nada.kth.se (Jon W{tte)
Organization: Royal Institute of Technology, Stockholm, Sweden
Lines: 38


Re: Virtual disks (Really, delayed-action disks)

I have two things to say about the post about "Virtual disks":

1) That's not virtual disks, that's just an extension of what the finder
   does to off-volume volumes/windows. Multiple partitions on a single
   hard disk is closer to what I'd call a "virtual disk".

2) It's TOO insecure. If the machine happened to go down AFTER you
   dragged around a file (or deleted it) but BEFORE these actions
   were updated, you'd end up having a corrupted file system and
   possible loss of data. This is especially true of a machine without
   protected memory... (Hear me, Apple ? :-)

Consider the following scenario:

The user puts in a disk, and the Mac remembers the disks directory structure.
The user ejects this disk and inserts another disk.
The user drags an icon from the last disk to the first.
The mac caches up this copy, but delays it.
The user drags the original file down the drain.
The mac caches up this action. Since the volume is on-line now, the mac
    promptly erases the file, after caching in the file data to be copied.
The power fails...

Or, if you tried to implement it a little safer, you could still end up
with corrupted file systems, file chains, directory entries etc.

I'm not saying that this doesn't happen now (It sadly does) but that there'd
be no use in increasing the chances for this to happen.

Since I feel that many more people will answer this in a similar vein, I
consider this 'nuff said.

-- 
This is your fortune from h+@nada.kth.se:
TANSTAAFL, rel. -- There Ain't No Such Thing As A Free Lunch