The default number of metadevices for a system is 128. If you need to configure more than the default, you can increase this value up to 1024.
When you add large numbers of metadevices, you may begin to see some system performance degradation only while administering metadevices (using DiskSuite Tool or the command line utilities). A large number of metadevices should not have an impact on normal system operation.
If you increase the number of metadevices to gain a larger namespace for partitioning the types of devices within certain numeric ranges, but you create fewer than 128 devices, you should not see any performance degradation. In this case, you should not have to add larger state database replicas.