[Simh] 3.8-2 rc2 Windows XP disk access issue

[Timothe Litt]

Villy,

The details that you posted look correct.  But I don't recommend changing
filelist.xml to exclude file types (or directories).  The filelist.xml
mechanism disappears in Vista and above -- and if you do serious work on a
disk, you don't want the VSS copy.  Even if not, on a notebook or older PC,
doubling the write traffic can be painful.  If you move to another system or
provide a copy to someone else, forgetting to update a hidden file is
likely.  And you run the risk (especially with file types) of unintended
consequences -- that is, not getting restore monitoring of something that
you want.

The simplest and best recommendation (which is the one in my previous note)
is "pick a safe extension for disk images".   Fighting the M$ OS isn't worth
the trouble - given the simple work-around of using a file type (extension)
that won't upset the OS.  Since the name of the disk image is only visible
to the simulator (and not the OS/applications running on the simulator), the
scope of the restriction is minimal.

I pointed to FileList.xml as the definitive list of file types to avoid in
XP.  I strongly recommend that it NOT be edited.  Just pick a different type
- simple, quick & safe...

I suppose a windoze-specific check could be placed in the SIMH attach code
to emit a warning if a (writable) disk image that is monitored by system
restore is selected.


But a few lines in the FAQ would probably suffice.  E.g. "Under windows XP
and above, excessive (system-crippling) disk activity can be caused by disk
or tape image files that are monitored by the System Restore facility.  Use
a file type (extension) such as ".simh-disk-image" to avoid this problem.
The list of file types to avoid is in %windir%\system32\restore\Filelist.xml
under Windows XP, and can be found in
http://msdn.microsoft.com/en-us/library/windows/desktop/aa378870(v=vs.85).as
px for later OS versions."


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-----Original Message-----
From: simh-bounces at trailing-edge.com [mailto:simh-bounces at trailing-edge.com]
On Behalf Of Villy Madsen
Sent: Saturday, March 17, 2012 12:09
To: 'Mark Benson'
Cc: simh at trailing-edge.com
Subject: Re: [Simh] 3.8-2 rc2 Windows XP disk access issue

I ran into this issue abt 3 yrs ago.

Here is the definitive answer from someone named Brian 

If someone wants to do an experiment, here is the information I have about
the way to change the list of files covered by System Restore on Windows XP
and Vista.

On XP, there is "super-hidden" file named
\windows\system32\restore\filelist.xml that specifies the file types and
directories covered by System Restore.
This file has the System, Hidden and Readonly attributes set. Log on as an
Administrator and in a Command Prompt window type:

   cd \windows\system32\restore
   attrib -s -h -r filelist.xml
   notepad filelist.xml

This file has elements named <FILES> and <DIRECTORIES> and <EXTENSIONS>,
with <Include> and <Exclude> elements within each. Not too hard to decypher.
I don't know what extension you're using for your VAX disk images, but I see
that DSK is listed in the <EXTENSIONS><Include> section.

So -- if someone wants to experiment with this on XP, how about excluding
the directory that contains your VAX disk images by adding a new <REC> entry
inside <DIRECTORIES><Include>, in the form <REC>c:\path\to\vax\files</REC>.
Also, be sure that System Protect is ON on the drive that holds your VAX
disk images.

Restart XP, log on as an Administrator, and request that it take a System
Restore point by following these steps:

1. Click Start, All Programs, Accessories, System Tools,
   System Restore.

2. Select Create a Restore Point and click Next

3. Enter a description e.g. "Test after excluding VAX directory"

4. Click Create

Wait until disk activity ceases, then try running the VAX simulator. Does
the disk activity problem occur?

On Vista, System Restore, and on Business/Enterprise/Ultimate, the Complate
PC Backup and "Previous Files" features, are handled by the Volume Shadow
Copy service, so entire files are not copied all at once as on XP. Original
versions of changed blocks are archived one at a time. 

Technically, you can't guarantee exclusion from coverage by System Restore
on Vista, since the backup occurs at the block level, below the file system.
But you can "advise" it to try to avoid specified files. It's done in the
registry under
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotTo
Snap
shot

There is probably no no compelling reason to try to exclude the VAX disk
images from coverage under Vista. Only changed blocks are copied so it won't
consume much time or space. I suppose if you ever restore the disks from
virtual tape, you'd be doing double the work there. 

I'd be interested in knowing if this does turn out to be the answer to the
VAX disk activity issue.









-----Original Message-----
From: simh-bounces at trailing-edge.com [mailto:simh-bounces at trailing-edge.com]
On Behalf Of Mark Benson
Sent: March 17, 2012 15:15
To: simh at trailing-edge.com
Subject: [Simh] 3.8-2 rc2 Windows XP disk access issue

I appear to be having a bit of a problem with SimH VAX 3.8-2 rc2 and disk
image access. I am using an old PIII 933MHz duel CPU workstation with 1GB
RAM and XP SP2. I have the required VC++ Runtimes installed and Winpcap. I
sourced the binaries from Mark Pizzolato.

I have run it using a fresh RA90 disk image attached at RQ0 (generated by
the emulator on startup). It boots from a VMS 7.3 ISO fine but when I try
and do any heavy lifting from the disk image, like restore the 7.3 save_set
to it form the CD using 'backup' it'll eventually error out (VMS backup
reports the device is not writable) and the emulator will stop dead and the
disk will be flat out with activity, but no CPU usage and nothing else going
on in Windows. I can only get it to stop by restarting Windows XP (at which
point VAX.exe eventually dies and the machine reboots). I have no Anti-virus
on the machine as it's only used for DEC related stuff, I don't surf the web
on it or read my e-mail (in short there's no malware on it either). 

I've surfaced scanned the physical hard drive in the machine and it appear
to be error free, it seems the emulator. I have had no other issues with
installing software, copying and moving files etc. I'm kinda stumped.

Any ideas?

-- 

Mark Benson

http://DECtec.info
Twitter: @DECtecInfo
HECnet: STAR69::MARK

Online Resource & Mailing List for DEC Enthusiasts.

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