4. PowerDNS Recursor performance

4.1. Recursor Caches

To get the best out of the PowerDNS recursor, which is important if you are doing thousands of queries per second, please consider the following.

Following the instructions above, you should be able to attain very high query rates.

4.1. Recursor Caches

The PowerDNS Recursor contains a number of caches, or information stores:

Nameserver speeds cache

The "NSSpeeds" cache contains the average latency to all remote authoritative servers.

Negative cache

The "Negcache" contains all domains known not to exist, or record types not to exist for a domain.

Recursor Cache

The Recursor Cache contains all DNS knowledge gathered over time.

Packet Cache

The Packet Cache contains previous answers sent to clients. If a question comes in that matches a previous answer, this is sent back directly.

The Packet Cache is consulted first, immediately after receiving a packet. This means that a high hitrate for the Packet Cache automatically lowers the cache hitrate of subsequent caches. This explains why releases 3.2 and beyond see dramatically lower DNS cache hitrates, since this is the first version with a Packet Cache.