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QEMU – A Crucial Building Block in Digital Preservation Strategies Klaus Rechert, Dirk von Suchodoletz, Achille N. Tchayep University of Freiburg, Germany
Digital Objects: A Risk Analysis
§ Physical Risks - Due decay of media (especially unprotected media like
CDs/DVDs) - Deprecation of connectors and standards
§ Technological Risks - Even with succesful bit-preservation rapid changes in
technological environment • Changes in (G)UI concepts, hardware architectures and
OS - E.g. IBM-8088 PC/XT à iPad
• Old (proprietary) file formats - E.g. WordStar, Lotus AmiPro, AutoCAD ...
§ Intellectual Risks - Changes in contextual knowlegde
• Missing / incomplete documentation • Lost context for single dig. objects.
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From Risks to Solutions
§ Research Domain of Digital Preservation pretty young but differentiates into sub domains
§ Our specialization is preservation action: à Emulation
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Dynamic Digital Objects
§ Objects like - Applications - Operating systems - Databases
§ Non-linear, user inter-action, multiple views
§ Not many options: - Print source code,
adaption to recent environments
- Video-recording, screenshots of game or application session
- Emulation
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Emulation as Digital Preservation Strategy
§ No changes on object, but reproduction of original environment - Emulators around for quite a while, supplemented
by virtualization - Can operate on different layers of software/
hardware stack - Number of objects to cover differs significantly;
thus hardware layer seems very attractive to focus on
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Emulation as Digital Preservation Strategy
§ More complex approach involving larger number of additional software components, complexities: - Standalone emulation is not sufficient - Different sectors of ongoing research - Several open issues
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Access to Emulation
§ DP emulation services should allow - to view digital objects and
compare digital objects in their original environment,
- to experience ancient (graphical) interactive user environments,
- to document and preserve of user interactions and interactive processes in ancient user environments,
- to migrate files using the original application in emulation in an automated way.
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QEMU as a Digital Preservation Tool
§ QEMU is „digital preservation aware“ through abstract interaction interfaces: - VNC
• Remote emulation services • Automation of interactions (replay)
- Migration-by-emulation - Automated testing
- monitor-Interface • Offers controls like power/reset-button • Load / eject removable media (floppy/CD-ROM)
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QEMU as a Digital Preservation Tool
§ Open Challenges: - For large scale preservation tasks, preservation
planning tools like PLATO are used for cost estimations.
à Use QEMU to measure and predict costs of large scale DP-preservation tasks
• Predict CPU-time/wall-clock time (on host system) • Memory consumption etc...
- Usability of QEMU monitor interface needs improvements:
• Operate complete guest session by sending sequences of keystrokes and mouse events.
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Preserving Emulated Hardware
§ Digital preservation depends on stable virtual machine hardware - Bridges the widening gap between digital past and
todays current environments. • E.g. DRDOS, Windows 3.x/95/NT, OS/2 are not
maintained anymore à no support for new (virtual)hardware, especially network and video.
à Reproduction of old software environments depends on emulators like QEMU providing necessary hardware configuration. E.g.:
• x386 ISA bus machine • NE2000 network adapter • Soundblaster 16 • Simple VGA
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Preserving Emulated Hardware
§ QEMU has a pretty good history of maintaining once introduced hw-components.
§ However: - Support for older Windows versions was rocky
• For some floppy support did not work • Some versions could not start Windows 9X at all • Mouse support affected by migration from Bochs to
SeaBIOS - Other major issues
• Currently Cirrus Logic VGA is unusable in Windows 3.11
• PIIX3 IDE not recognized by Windows 95 and official drivers
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(Automated) Regression Testing
§ Software testing in general is a difficult task. § As we are interested in preserving support
for old systems we propose a pragmatic approach: - Black-box testing:
• Booting from different media • Checking screen resolution, network, keyboard
and mouse functionality • Booting various (old) OS. Check if they operable
for defined tasks • Start applications and execute actions
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(Automated) Regression Testing
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Test Example
§ Test Case - Boot Windows 3.11 image from harddisk - Install Lotus Ami-Pro from CD - Test case was recorded on qemu-10.6
§ Tested Emulators - qemu-11.1, qemu-12.4, qemu-12.5, qemu-13.0,
qemu-14.0 § Result
- Test failed with qemu-12.4, qemu-12.5 - Reason: no mouse control through VNC
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Challenges and Chances
§ QEMU faces same problems like other digital objects: feature development and updates - without changing the API to original host environments - “stable” virtual hardware
§ Integration into digital preservation frameworks: - to automate procedures to be run on thousands of
objects § Definition of a proper feature set for
preservation-aware emulators - E.g. expose internal behavior
§ (Automated) Regression testing for old systems - Leveraging the growing emulation user community in
digital preservation (e.g. comprehensive software archive)
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Thank you for your Attention!
Questions / Comments?
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Klaus Rechert Chair in Communication Systems Faculty of Engineering University of Freiburg / Germany [email protected]