AIDA64 Random Access Time
Version and / or Patch Used: 1.60
Developer Homepage: http://www.aida64.com
Product Homepage: http://www.aida64.com
AIDA64 offers several different benchmarks for testing and optimizing your system or network. The Random Access test is one of very few if not only that will measure hard drives random access times in hundredths of milliseconds as oppose to tens of milliseconds.
Drives with only one or two tests displayed in the write test mean that they have failed the test and their Maximum and possibly their Average Scores were very high after the cache fills. This usually happens only with controllers manufactured by Jmicron.
The Samsung 840 EVO 750GB and 250GB both share the same read data access times of .11 in this test.
We think when Samsung moved to their new 19nm process for TLC, they also doubled the capacity of the die to 128Gbit. We're seeing an increase in write latency with the new EVO, just like we did with M500 when Micron moved to new 128Gbit dies.
Here we see the test with RAPID enabled, so we can walk though some of this. The first thing to understand is that in a consumer / client environment, you will never write the entire capacity of the SSD all at one time. Several reviews will be published today using IOmeter where reviewers are looking for steady state performance either in MB/s or IOPS. Those tests have zero validity in consumer SSD testing simply because you will never write 500GB of data to a 250GB SSD as fast as you can with a client workload.
With that said, let's look at the graph. At the beginning you see RAPID, then the SLC layer and then TLC latency. After the third step up from the left, the drive starts garbage collection, and the latency increases. Further to the right, it appears that the 840 EVO starts a more aggressive GC scheme and that increases latency even further. By the time that happens, we've already wrote 325GB of data to the drive as fast as we could. I'm not going to say that's impossible, but in order to do it, you have to transfer six and a half Blu-ray ISOs to the drive back-to-back.