[Simh] Excess IOs running SIMH on Windows/XP

[Villy Madsen]

Well - the proof is in the eating!!
The sim ran all through the night, and logged millions of write bytes!!
Millions as opposed to billions!!

I can't see anywhere obvious where I can specify the extensions of the file to
"be protected" - but doesn't really matter.  I have configured a seperate
partition for the VAX and just disabled the restore point for the entire
partition. ( I will check at work - where we are running professional and see if
the restore point options are the same!)

I wonder how many other's have been bit by this....

So many times, I thought that it had been fixed - the massive IO crunch was not
happening at startup or shutdown - or not always or....  But running it for a
longer time almost always showed massive amounts of write IO charged - enough
for at least a byte for every vax disk byte - and sometimes multiples of this...

Not this time.  I think we have the smoking gun this time....
(and it seems to start up quicker to - but that's probably just wishful
thinking!)

Villy


 

-----Original Message-----
From: simh-bounces at trailing-edge.com [mailto:simh-bounces at trailing-edge.com] On
Behalf Of Brian Knittel
Sent: Thursday, January 24, 2008 23:23
To: simh at trailing-edge.com
Subject: Re: [Simh] Excess IOs running SIMH on Windows/XP

Oh my goodness. Is the extension of the disk image file file one of the
extensions monitored by System Restore?
System restore could indeed be the culprit. On XP, when a "restore point" is
made, nothing is actually backed up at that moment. When an attempt is made to
modify a protected file later on the, entire file is copied to the Restore
Point's folder under System Volume Information.
This is handled by a file system filter driver that monitors file open calls.

That indeed could be the cause of the disk activity when the simulator is
started up, which has been discussed for a couple of years here. The symptom is
that the entire disk image appears to be read, right?

Does this activity happen every time the sim is started, or just once a day more
or less (e.g. after the automatic daily system restore point is made?).

There is a registry entry that you can use to exclude files.
If this indeed what the issue is, we can address it pretty quickly.

Vista by the way uses volume shadow copy to perform system restore points and
"complete PC Backup" on the business/enterprise/ultimate versions. These won't
cause the bulk copy but will copy on a block by block basis as files are
changed.

Brian




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