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From: gaynor@agvax2.ag.ohio-state.edu
Subject: Re: SE/30 VM trouble in System 7
Message-ID: <1991May29.173052.17108@zardoz.eng.ohio-state.edu>
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References: <2842d41f.4648@petunia.CalPoly.EDU> <1991May29.125650.16389@zardoz.eng.ohio-state.edu>,<53439@apple.Apple.COM>
Distribution: usa
Date: Wed, 29 May 1991 17:30:52 GMT

In article <53439@apple.Apple.COM>, blob@Apple.COM (Brian Bechtel) writes:
>gaynor@agvax2.ag.ohio-state.edu writes:
>>In article <2842d41f.4648@petunia.CalPoly.EDU>, mjohnson@cosmos.acs.calpoly.edu (Mark S. Johnson) writes:
>
>>[stuff about how 5MB of VM eats 10MB of disk space]
>
>>Yep, that's the way it is.  2 MB of VM eats up 4 MB on my HD.  
>
>No.  VM uses 1 MB of hard disk for each MB of memory, with ALL memory
>counting towards the total.  If you ask for 15 MB of memory, then VM
>takes up 15 MB of disk space, no matter how much RAM is in your
>computer.  If you specify 12 MB on an 8 MB RAM SE/30, you create a 12 MB
>invisible file called "VM Storage".

Well, then in an odd sense I was right.  Note, Brian, that I said 2 MB
of -VM- eats up 4 MB on my HD.  I also have 2 MB of RAM.  Thus, 4 MB
for "VM Storage".  It also makes sense for Mark - he has 5 MB RAM, 5
MB VM, so a 10 MB VM file.

I had been wondering why a 1 MB VM setting took up 3MB for the VM
storage file.  Now I at least know the equation.

Brian, could you enlighten us a bit as to why it works in this
fashion?  I mean, it seems odd to me that, according to what you've
just said, someone with 8 MB RAM who added 1 MB VM (for 9 MB total)
would have a VM Storage file of 9 MB in size.

From this, it would appear that Virtual Memory, even in small
portions, would require -huge- amounts of disk space for those with
large amounts of RAM.

---
Jim Gaynor - AgVAX System Manager - Academic Computing - Ohio State University
VMS:<gaynor@agvax2.ag.ohio-state.edu>  UNIX:<gaynor@magnus.acs.ohio-state.edu>
Disclaimer : All opinions expressed here are mine and only mine.  So there!
Witty Quote: "Think, think, think, think..." - Winnie-the-Pooh, Taoist Bear.
