Capacity:
Raw capacity
Total amount of stored information that a medium or storage device can hold is expressed as a quantity of bytes and bits (for example 10.4 megabytes).
Memory storage density
The density of stored information is the storage capacity of a medium divided with a unit of length, area or volume (for example1.2 megabytes per square inch).
Performance:
Latency
Time ,taken by it to access a specific location in storage. The relevant unit of measurement is usually nanosecond for primary storage and millisecond for secondary storage, & second for tertiary storage. It may make sense to separate write latency and read latency, and in case of sequential access storage, maximum, minimum and average latency.
Throughput
The rate at which information can be read from /or written to the storage. In computer data storage the throughput is typically expressed in terms of megabytes per second or say MB/s, though bit rate can also be used. As with latency, write rate and read rate may require to be differentiated. Accessing media sequentially, as opposed to randomly, usually yields maximum throughput.