As my HDD slots run out, I relocated one of my SSD drives of the cache pool to CD-ROM slot. Later on, I realized that CD-ROM SATA is 3Gb/s. All the hard disks as well as the other SSD cache have 6Gb/s.

 

Does it create any bottleneck relocating SSD cache drive to 3Gb/s SATA connection?

Normally not. For networking, you need a 10Gbit/s interface to be able to saturate the SSD. With gbit networking, you need a lot of Docker/VM activity that fights for the bandwidth to notice any difference. The most important thing with SSD isn't the bandwidth but the number of I/O operations/second.

Thank you @pwm.