SSD roundup: Vertex 3 vs M4 vs C300 vs 510 vs 320 vs x25-M vs F120 vs Falcon II

[johnw]

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.

Thanks for posting that observation. That might explain something that I have been wondering about since the first reviews of the V3 came out. With CDM, the 4KB QD1 random reads are around 35 MB/s, but with AS-SSD, they are only 20 MB/s. With your observation, this could be explained by AS-SSD performing random reads over a larger span than CDM.

Or maybe not. I think AS-SSD uses a 1GB test file, and CDM is often run with a 1GB test file, which would suggest that the spans are not the source of the discrepancy. I suppose AS-SSD might use full-span for random reads (ignoring its test file), since for reads, the test file is not necessary. But I don't know. Maybe this could be determined with hIOmon? Does it record the LBAs that are accessed?