MS-DOS 6.22 Drive Write Monitoring Utilities

In MS-DOS 6.22, continuous monitoring of system drive write operations is primarily accomplished using the memory-resident utility VSAFE for security and unauthorized write detection, alongside SMARTMON for real-time tracking of disk cache write performance. This article explains how these utilities monitor drive write operations, their technical configurations, and how to utilize them within the MS-DOS environment.

VSAFE: Real-Time Write Interception and Protection

VSAFE is a terminate-and-stay-resident (TSR) program included with MS-DOS 6.22 designed to continuously monitor system activity, specifically intercepting attempts to write to physical and logical drives. By monitoring low-level disk interrupts (such as INT 13h and INT 21h), VSAFE detects and blocks write operations before they alter critical disk sectors or executable files.

Key Monitoring Functions in VSAFE

VSAFE can be configured with specific flags to control how it monitors drive writes:

  • Option 1 (/1+): Warns of formatting attempts on the hard disk.
  • Option 3 (/3+): Prevents programs from writing to disk entirely.
  • Option 6 (/6+): Continuously protects against write operations targeting the hard disk boot sector or partition table.
  • Option 7 (/7+): Protects against write attempts to the floppy disk boot sector.
  • Option 8 (/8+): Intercepts and warns against write operations targeting executable files (.EXE, .COM).

Loading VSAFE

To initiate continuous monitoring from the command line or within AUTOEXEC.BAT, enter:

VSAFE /6+ /8+

When a program attempts a write operation matching the active protection flags, VSAFE halts the execution and displays an alert overlay, allowing the user to permit or deny the write access.

SMARTMON: Continuous Write and Cache Activity Tracking

While VSAFE provides write monitoring for security and integrity, SMARTMON (SMARTDrive Monitor) is the MS-DOS 6.22 companion utility that provides continuous visual monitoring of drive write performance and cache activity.

SMARTMON runs in conjunction with SMARTDRV.EXE (the DOS disk caching utility) within a Windows 3.1 environment running on MS-DOS 6.22:

  • Write Monitoring: Displays real-time percentages of read/write cache hits and tracks writes committed to physical disk sectors.
  • Write-Buffering Control: Allows users to observe and manage write-caching behavior, distinguishing between buffered delayed writes and immediate write-through operations.

To load the underlying write-caching driver in DOS:

SMARTDRV.EXE C+

The C+ parameter enables write caching on the designated drive, allowing write operations to be monitored and managed by the driver.

Summary

For monitoring and preventing unauthorized write operations to critical drive areas, VSAFE serves as the continuous watchdog in MS-DOS 6.22. For continuous operational monitoring of disk write performance and caching metrics, SMARTMON paired with SMARTDRV provides the necessary real-time tracking.