Why Anti-Virus Software should not be Deployed on Charon Emulator Hosts
Table of contents
Problem Description
Stromasys strongly recommends to not run anti-virus software on Charon host systems.
Running anti-virus software can cause severe problems for the emulator, in particular, if this software scans files used as virtual storage devices by the emulator (vdisks, vtapes, ISO files).
What happens when running an antivirus scan on an active emulator vdisk?
- The anti-virus software reads the whole vdisk (typically many gigabytes) during the scan.
- This causes competition for I/O, memory, and CPU resources on the Charon host system.
- It also causes competition for access to the file itself between the anti-virus software running on the host and the guest system running in the emulator.
What are the consequences of the competition for resources between the emulator and the anti-virus software?
- Timing-sensitive guest operating systems, such as OpenVMS, may crash if the I/O response time is increased due to the activities of the anti-virus software. Such a crash, in addition to causing an outage, may also lead to further problems, such as data corruption on the virtual storage device.
- Even if there is no crash, there may be a severe performance degradation for the overall system including the emulator, the guest system, and the users of the guest system.
Other possible negative consequences:
- Should the anti-virus system mistakenly identify a virus in a virtual storage device, such as a vdisk, it could disable access to this file and thus also lead to guest system crashes, data corruption, and longer outages.
Files to Exclude if the Use of Anti-Virus Cannot be Avoided
Stromasys strongly recommends to not run anti-virus software on Charon host systems.
Should it be required for some reason to run such software on a Charon emulator host, ensure that any files/devices presented to the emulator as storage devices are excluded from all scans performed by the software:
- vdisk files: files presented to the emulator as physical disk devices
- vtape files: files presented to the emulator as physical tape drives
- ISO files: files presented to the emulator as physical CD-ROM devices
- physical disk partitions passed-through to the emulator as physical disks
Problems with Other Types of Security Software
Some security software, for example, Symantec Endpoint Protection (SEP) , can affect the running of the Charon emulator software in very different ways. Examples: by modifying executable files, or by loading libraries that supersede the original system libraries. An example is described here: Charon-AXP/VAX/PDP on Windows fails with exception code related to SYSFER.DLL.
Recommendations:
- Disable the security software.
If this is not possible:
- Exclude the Charon installation folder from being included in the actions of the security software, and also the folders containing the Charon virtual disks if there are.
- Create application control exclusions for the Charon executable files.
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