Also, an internal RAID controller is usually less expensive than a comparably equipped external controller. There are some major disadvantages to an internal controller. First, if the controller fails, then the host computer must be shut down to repair or replace the board. If an external RAID controller fails, simply turn off the other devices on that bus. Second, most internal controllers do not have expansion cards, so the size of the RAID set is limited.
External controllers offer more flexibility in the number of drives it can address.
Third, only one host can talk to an internal controller. Fourth, failover on an internal controller is difficult at best to configure. Benchmark A known benchmark is used to compare the performance of variuos RAID systems. The RAB has developed and reviewed several benchmarks suitable of creating data derived solely on the merits of the RAID controller, and not the test environment. All three tests are available free from various sites and relatively easy to setup and run.