Quote Originally Posted by Ao1 View Post
If you only read/ write across a limited span on the SSD you get very good results. Wear levelling can kick in. If you read/ write across the complete span of the SSD it will really struggle. Off the top of my head Intel give specs based on an 8GB span. They also now give data for performance across the full span and IOPs drop like a stone. 300 or 400 from recollection.

If you write lots of small files and then overwrite them I think it also slows things down when compared to over writing larger files.

Benchmarking SSD's is a nightmare.
1st ... sorry for my very bad english

The problem here is with Vertex 3 only, from what i've see yet. Perhaps SandForce SF-1200 to but i haven't tested.

Random Read 4KB on M4 256 GB (for example) is 58 MB/s on QD3 even if you test it on 1 GB file, 8 GB file (and so on).
Random Read 4KB on Vertex 3 240 GB is 72 MB /s on 1 GB file, 72 MB/s on 2 GB file, 52 MB/s on 4 GB file, 44 MB/s on 8 GB file and 44 MB on 16 GB file.

In this case the size of the file = the size on the NAND since i use incompressible data on IOMETER (random)

But if you use highly compressible data (not very realistic, but ...) , with a 8 GB file you get 74 MB/s. Why ? Because the 8 GB file is higly compressed by the SandForce, and perhaps take something like 2 GB of real nand or less.
You didn't test random access on 8 GB but on something like 2 GB.
If i test random access within 45GB file of highly compressible data for example i get 45 MB/s.

The fact is that if you compare random read of Vertex 3 vs M4 using a (very) small portion of the SSD, then Vertex 3 show better random read than M4. But on a bigger part of the SSD, the M4 is faster.

For me, performance on a very small part of a SSD is less important. Random read is important for heayy multitasking, and heavy multitasking could need to read data from a large part of the SSD.