[Info-vax] VMS port to x86

[Paul Sture]

On Tue, 27 Mar 2012 09:42:02 -0600, Bob Koehler wrote:

> In article <4f70d44f$0$1746$c3e8da3$92d0a893 at news.astraweb.com>, JF
> Mezei <jfmezei.spamnot at vaxination.ca> writes:
>> 
>> Anyone know what VMware really is ? It wouldn't susprise me if it had
>> linux under the hood.
> 
>    I think VMware is a product line.  I know we're using it to host WXP
>    on top of Mac OS.  Since they're both Intel user mode code on WXP
>    simply runs as user mode code on the CPU.  Adds I hear for VMware
>    imply other, quite different products.

Yes, VMware has a family of products.  The one you are running on Mac OS 
X is probably (but not necessarily) VMware Fusion.

It does add its own networking and allows you to talk to peripherals 
which are only supported by Windows:

http://www.vmware.com/products/fusion/overview.html

>    For us, VMware has to intercept WXP access to the underlying
>    hardware, and simulate interrupts from hardware, but I don't suspect
>    anyone of tossing a whole Linux kernel in there just for that.

It's probably hosting a virtual disk for the Windows system, easy to back 
up, and will have snapshot facilities so you can roll back to a known 
good point-

I have used the equivalent (known as VMware Workstation) on Windows and 
Linux hosts.  I am not sure how much that differs from the Mac version, 
but you can seamlessly integrate desktops, make movies of your work adn 
so on.  VMware also has the means to build comprehensive virtual 
networks, handy for those who want to test them out before deploying.

I did find a couple of performance problems with it *for my environment*:

a) It uses its own pagefiles. The advantage here is that you can have
   n virtual machines which have total RAM exceeding the amount on
   the host system.  The drawback for me was that it used these pagefiles
   even when I had plenty of real RAM free, and it slowed things up too
   much.

b) It has its own allocation algorithms for hosted virtual disks, and
   functionality to defragment these.  You still have to do any
   defragmentation that the Windows virtual machine requires itself
   though.

Point a) is what persuaded me to look elsewhere on my hardware, I got 
sick of the system grinding to a halt with the disk activity light on 
solidly.  I chose VirtualBox.

If you have the right combination of disks attached to the host, you can 
set your virtual machines to use them as raw devices by their O/S.

I also looked at different Linux file systems when I was looking at VMware 
Workstation.  I wasn't particularly happy about the performance I got 
with any of them*, and believe it or not, I ended up concluding that 
Windows as a host provided me with better performance and a more stable 
experience.

* I might try this again now that more work has been on of btrfs and XFS. 
Those interested in file systems might wish to have a look at a couple of 
presentations on these at a recent Australian Linux conference:

"I Can't Believe This is Butter! A tour of btrfs. - Avi Miller"

http://www.youtube.com/watch?v=hxWuaozpe2I

"XFS: Recent and Future Adventures in Filesystem Scalability - Dave 
Chinner"

http://www.youtube.com/watch?v=5XDTQLa3NjE

Be ready with the pause button for these videos, as the video editor had 
the unfortunate tendency to switch away from the slides before the 
speaker had got to every point.

And to get the best enjoyment out of the XFS one, do watch the btrfs one 
first so that you understand the bit at the end where he criticies btrfs 
performance :-)

-- 
Paul Sture