ISPPlanet Cache Review Series - NetApp NetCache C720

Tuning Your Web Cache

Fine-tune your cache using the Object Settings and Caching Rules pages (right). Non-cacheable objects are identified by URL substring or MIME type; cacheable cookies are identified by file extension. Specified URLs can be redirected, and TTL processing can be tweaked. When an object expires, the NetCache verifies its last modified time on the next request.

For objects without an explicit TTL, the NetCache calculates a default TTL based on last modified time. In this way, a very static object should get a long default TTL without frequent re-verification. But while testing this feature, we found an old zip file was downloaded from the origin server several times before a cached copy was vended. Network Appliance is investigating.

 

The Network Settings page (left) provides tuning knobs that enable persistent connections, quick abort, X-Forwarded-For MIME header privacy, and passive FTP. Incoming requests can be denied for specified ports, and outbound ports can be limited for increased security. Traffic types can be bound to interfaces, and outgoing requests can be distributed across IPs to reduce response congestion.

Cache hierarchy rules can be refined by defining local domains and domains that lie inside a proxy firewall.

The Administration Guide offers tips for tuning your web cache to increase hit rate, improve response time, and optimize cache performance. You'll find information for tuning in the UI Monitor section (right).
	The Monitor "home" page provides overall stats—hit rate, requests per hour, disk usage, fetch time. An Information Summary (left) offers further detail, backed up by rigorous Network, Object, and IP Cache Instrumentation pages. Any page can be configured to refresh every few seconds or minutes for continuous view.
The detail found here is exceptional: for example, the Object Instrumentation page (right) sums stored objects by reference count, size, and TTL. But be prepared to do some number crunching: this data isn't graphed.