Now let’s see what changes as soon as we shift from firmware 3.00 to firmware 3.01:

ST380023AS with 3.01 firmware and Promise SATA 150 TX2 Plus (WB)

As we see, the test behaves just a little bit differently now. The only difference s that we can now see separate peaks on the write speed graphs (it is probably because the entire buffer can no longer be used for writes…). However, the upsurge in the beginning of the tests is still there and the write speed remained not very high.

And now we will change the work mode of Promise SATA 150 TX2 Plus controller into WT (Write Through) with the help of Cache Config utility. This should slow down the processing of all write requests:

ST380023AS with 3.01 firmware and Promise SATA 150 TX2 Plus (WT)

Well, this changes the entire picture completely. Look how big the write speed now is!

Since the HDD buffer is now filled with 32KB write requests, it gets filled and emptied in a much smoother way.

To make sure that it is not SATA interface or tricky Promise drivers that speed up the writes, let’s have a look at the next three graphs. We will begin with the results shown by SATA 80 HDD with SiliconImage controller:

ST380023AS with 3.01 firmware and SiliconImage CP3112SATA150

As you see, the graph is very much like the previous one. Replacing the controller didn’t tell on the way HDTach worked. Now let’s try to completely change the HDD being tested. We will take a regular ATA/100 hard disk drive, in our case it will be Seagate Barracuda ATA V 120GB (ST3120023A) with 2MB buffer, and a Promise Ultra100 TX2 controller:

ST3120023A with 3.31 firmware and Promise Ultra100 TX2

The write speed become quite normal, i.e. not very high. Could it be the cache buffer size then that affected the results? No problem, let’s check it out. We take an ATA/100 HDD with 8MB cache-buffer:

ST3120024A with 3.33 firmware and Promise Ultra100 TX2

This is where the story comes from! :)

About a year and a half ago I had an argument with one of my colleagues about the influence of the cache-buffer size (and its structure) on the write speed measured by HDTach test. I hope he is reading this review now :)

Well, the only thing left, which we should also check is the CPU utilization as measured by HDTach. Among all the HDD + controller combinations tested we would like to point out only one: SATA 80 (ST380023AS) + Promise SATA 150 TX2 Plus working in WB mode. The CPU utilization in this case appeared about 3 times as high as by all other testing participants.

Summing up the results obtained, we would like to point out the following. With the testing methodology applied by HDTach Seagate drives with 8MB cache-buffer demonstrate better results than HDDs with 2MB cache-buffer. We would also like to stress that it is still too early to claim that the interface type (namely ATA or SATA) affects the performance.

Well, we will try t imitate read and write benchmarks ourselves then, with the help of the excellent Intel IOMeter utility :)