If you think that your storage device is slow, first step is to check linear read speed, disk access time, and IOPS for the device.
Any benchmark software can give you all the mentioned performance characteristics. Searched the web, I saw both paid and free tools to benchmark data storage devices. I used non paid and simple benchmark software - BenchMe - which gives linear read speed in real time. The free benchmark tool also produces a chart with distribution of access time measured for the data storage device.
On top of that, BenchMe free benchmark software provides a list of features the data storage device supports. It is worth to visit the vendor site to have a look at sample benchmark charts for RAID arrays, SSDs, and hard drives. The only minus I 've come across is that the tool doesn't handle hard disks connected via USB.