How does LVM Mirror read from and write to each mirror legs?

Issue

• Our customer wants to know the behavior of LVM mirroring.

  1. When write data to LVM mirror, How does the system request the I/O to each PV?

     • write data to each mirror legs at the same time?
     • write data to one mirror leg, and copy to the other one?
     • other processing?

  2. When read data from LVM mirror, How does the system request the I/O?

     • read data from one mirror leg only?
     • read data from each mirror legs doubly?
     • read data from each mirror legs without duplication using some kind of algorithm?
     • other processing?

  3. The difference of throughput between LVM linear mode and mirror mode.