As for throughput, when estimating the latency overhead associated with DRBD, there are some important natural limitations to consider:
- DRBD latency is bound by that of the raw I/O subsystem.
- DRBD latency is bound by the available network latency.
The sum of the two establishes the theoretical latency minimum incurred to DRBD. DRBD then adds to that latency a slight additional latency overhead, which can be expected to be less than 1 percent.
- Consider the example of a local disk subsystem with a write latency of 3ms and a network link with one of 0.2ms. Then the expected DRBD latency would be 3.2 ms or a roughly 7-percent latency increase over just writing to a local disk.
![[Note]](images/note.png) | Note |
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Latency may be influenced by a number of other factors, including CPU cache misses, context switches, and others. |