HDD Benchmark termonology

Hey Guys,

I have been reading a lot of reviews for SSD's recently and have been a little confused about what some of the benchmark results actually represent. I think I know most of them but thought I would ask you guys see if someone can set me straight.

Sequential Read Performance: This is the amount of data that can be read sequentially (continuous block) from the drive, measured in MB/s.

Sequential Write Performance: This is the amount of data that can be written sequentially (continuous block) to the drive, measured in MB/s.

Sequential read/writes are important if you are using your drive for storage as this is the behaviour exhibited when copying MP3's/avi's etc.

Random Read Performance: This is the amount of data that can be read randomly (non continuous block) from the drive, measured in MB/s. Often measured in IOPs

Random Write Performance: This is the amount of data that can be written randomly (non continuous block) to the drive, measured in MB/s. Often measured in IOPs. Important if you are using your drive as a boot/application drive as this is the behaviour that will most likely be exhibited.

Read Latency: Delay between the read request and the drive performing the action. Latency for both sequential read and random read.

Write Latency: Delay between the write request and the drive performing the action. Latency for both sequential write and random write.

Read Access Time: Not sure, is this the same as read latency?

Write Access Time: Not sure is this the same as write latency?

Read Burst Rate: The highest speed in which data can be transferred form the drive to the operating system on a read request.

Write Burst Rate: The highest speed in which data can be transferred form the drive to the operating system on a write request.

Transfer rates: Not sure are these the same as read/write performances?

Throughput: Something like the average rate of data transfer. So again, is this the same as the read/write performances?

I may just be being stupid. I mainly look at benchmarks form HDTune and Everest so it could just be two different ways of saying the same thing.

For most intents and purposes, "latency" and "access time" can be treated as synonyms. There are some technical nits you can get into as Sub Mesa mentioned, but if a review or poster mentions one or the other of these terms and doesn't go into any more detail, you can assume they mean the same thing.

"Transfer rate" and "sequential read" / "sequential write" rates are also essentially the same thing.

"Throughput" is a vague term because it's completely dependent on the kind of I/O load being measured - is it sequential, random, or a mix of both? Single stream of requests or multiple concurrent requests? Without further qualification it's not a very meaningful number.

You said:

...and in this I disagree. Random read performance, IMHO, is more indicative of OS boot performance since the OS disk is read from MUCH more often than it's written to.