Results: 4 KB Random Read And Write Performance
AS-SSD: 4 KB Random Reads and Writes
This benchmark is the most important for real-world performance, and the fastest hard drive just can’t compete with an SSD when it comes to 4 KB random reads and writes. Samsung's 840 Pro does a little bit better attached to a 6 Gb/s interface compared to the 3 Gb/s port. Its writes are 20 MB/s faster, while its reads are less than 2 MB/s quicker.
If we push higher queue depths, representing the number of outstanding commands the SSD is being asked to process concurrently, the faster interface does help bolster performance quite a bit. This is largely theoretical, though. No desktop environment is ever going to see queue depths of 32 or more.
With that context, we do see random reads and writes at least 1.5x faster on the 6 Gb/s port.
CrystalDiskMark: 4 KB Random Reads and Writes
CrystalDiskMark’s benchmark numbers tell a similar tale. The advantage of SATA 6Gb/s over the 3 Gb/s standard is relatively small at the low queue depths typical of most desktops, and then larger at the command queues seen in server environments. Again, if you're using a mainstream PC or notebook, you're really only worried about queue depths of one to four.
Iometer: 4 KB Random Reads and Writes
Iometer’s numbers differ a bit from the other two benchmarks, though the overall message doesn't change. Samsung's 840 Pro does quite a bit better attached to a 6 Gb/s port compared to SATA 3Gb/s, particularly in reads.