How to Use CacheDir (Cache Directory Tool) with Forefront TMG 2010

Streamline TMG Cache Management — Cache Directory Tool Best Practices

Overview

Use the Cache Directory Tool (CacheDir) to inspect and manage the Forefront Threat Management Gateway (TMG) web cache. Regular cache maintenance improves hit rates, reduces disk usage, and prevents stale content delivery.

Quick checklist

• Schedule reviews: Weekly for high-traffic servers; monthly for low-traffic.
• Monitor cache size: Keep below 70–80% of allocated disk to avoid eviction storms.
• Back up config: Export TMG/caching configuration before mass changes.
• Use read-only when auditing: Avoid accidental modifications during inspections.

Common tasks with CacheDir

1. List cached entries
   • Identify large or frequently stale objects.
2. Filter by URL, content-type, or age
   • Target images, scripts, or long-lived HTML separately.
3. Mark items obsolete
   • Force revalidation for content that must be fresh.
4. Export metadata
   • Create reports (URLs, sizes, timestamps) for trend analysis.
5. Delete selected entries
   • Remove malicious, broken, or space-consuming objects.

Best-practice workflow

1. Run CacheDir in read-only mode and export a full listing.
2. Analyze exported data for top-size and top-age candidates (sort by size/age).
3. Mark obsolete for items likely to have changed; delete only after confirmation.
4. Re-run listing to verify changes and record results for the next review.
5. If disk pressure persists, increase cache size or refine cache-control policies on origin servers.

Automation & scheduling

• Automate CacheDir runs and exports via scheduled tasks or scripts.
• Integrate report parsing to trigger alerts when large single objects or sudden growth is detected.
• Combine with log-analysis to correlate cache miss spikes with backend changes.

Safety & policy tips

• Prefer marking obsolete over immediate deletion when unsure.
• Coordinate with web/content teams before bulk removals.
• Enforce HTTP cache-control headers and versioned static asset naming to reduce need for manual invalidation.

Performance tuning

• Exclude rarely beneficial content types (e.g., large media) from cache or use separate cache stores.
• Tune object-size limits and max-age settings to balance freshness vs. hit ratio.
• Monitor hit ratio, latency, and disk I/O after changes; revert if user impact increases.

Quick commands (example)

• Export listing: use CacheDir’s export option to CSV.
• Mark obsolete: use CacheDir flag for target entries.
• Delete: remove selected cache files with CacheDir delete command (confirm before run).

If you want, I can produce a sample CacheDir command sequence and a small parsing script to automate exports and identify the largest cached objects.