HORM FAQ from Vegas

14 05 2006

After my presentation about "Hibernate Once Resume Many (HORM) – Boot Windows XP embedded in under 10 seconds!" at MEDC in Vegas some quite interesting questions have been raised, which, I think, might be interesting to other developers as well. So please see below my summary of our Q&A after the session.


Q: Is it possible to limit the size of the hibernation file?

A: No, it is not. The only way to limit the hibernation file is to reduce the size of the system’s physical memory.


Q: Will it be a problem to put the hibernation file in a different location than the boot partition?

A: Yes, absolutely. Windows boot loader expects the hiberfile to be on the boot volume.


Q: Why is it not a good idea to just re-use the same hibernation file in a HORM configuration, having EWF protected and unprotected partitions?

A: After the first boot from the hibernation file the data in the file and on disk gets out of sync with the first write access to disk. If one still reboots from an "old" hibernation file the system will see files that are no longer there (zombies) or will not see files that are there on the unprotected volume.

This is a good recipe for desaster. The solution is to umount all unprotected volumes before the creation of the hibernation file (see MSDN technical article). After booting from it, these volumes should be remounted.

Be aware, that one has stop any restart any applications using these volumesbefore/after the reboot, additionally.
Check out our free tool "HORM Manager Lite" which helps You to handle this situation.


Q: How do I configure EWF RAM/Reg Mode?

A: Ram/Reg mode can absolutely be recommended in HORM Scenarios. You can find a good descriptionon how to configure this mode in the Xpe documentation. See "Configuring EWF RAM Reg Mode" for more info. And yes, it is some manual work!

Tip: Build a custom component to have those settings at hand for further images and do not forget to disable the FBA COM/DLL registration resource in the EWF component.


Q: What is the file resmany.dat good for?

A: It is an empty file used as a flag for the Windows EWF bootloader. This flag indicates that the hiberfile must not be invalidated after a sucesful boot (as XP Pro does)


Q: Does HORM work with the standard NT loader?

A: No HORM requires the EWF NT loader. The normal loader just ignores resmany.dat and invalidates the hibernation file after booting from it.


Q: Why do I need EWF to enable HORM?

A: EWF guarantees that the OS partition does not change at all. This is the only way to keep hibernation file and partition data in sync. Therefore it is not possible to activate HORM without EWF turned on.


Still questions?

Drop me a line at info@wechsler-consulting.de 







5 responses

26 09 2006

When using HORM with a pagefile, how do I guarantee the pagefile is not being used when the hibernate file is created.
I have a system with 3 partitions, 1 is protected by EWF. Others hold log files, and pagefile.

13 06 2006

Jeff – bad luck. Nice really was worth the trip.
Well, maybe we will have a chance to meet at another occasion over here in Europe or the States.

11 06 2006

Unfortunately I didn\’t make it to Nice…  but would have LOVED to visit Nice, France.  So didn\’t get to meet you in France; I am based in the US.I have worked with several customer projects who have needed "instant-on" with XPe…  The /Maxmem switch is quite an useful debugging trick; I\’ve used it in a few scenarios that helped a lot…  At times EWF isn\’t very user friendly when tweaking settings; I haven\’t had a chance to try out HORM Mgr Lite, but I will have to.Jeff

11 06 2006

Thanks Jeff,
You are absolutely right and this is a great hint.
Was it You, I was talking to in Nice?

9 06 2006

FYI – When troubleshooting or testing HORM; the /maxmem switch used in the Windows boot.ini is an easy way to tweak the size of the hibernation file (hiberfile.sys) without physically removing or changing RAM present in your system…Jeff Chu | bsquarejeffc@nospam.bsquare.com

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