Quote Originally Posted by johnw View Post
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?
Hi johnw,

The short answer to both of your questions is "Yes".

Along these lines, please see the hIOmon thread post #297 where I used the hIOmon "I/O Operation Trace" feature along with the hIOmon "Summary" metrics feature in analyzing only the "Access Time" option of AS SSD.

The hIOmon "I/O Operation Trace" feature option enables you to collect, display, and export an individual record for each and every I/O operation for those I/O operations specified to be monitored by hIOmon. This "I/O Operation Trace" record can include the starting address (basically LBA in the case of device I/O operations) of the data transfer and the length of the data transfer.

The hIOmon software also provides an "Access Range Summary" option, which enables you to create a CSV-based export file where each record/row within this export file contains the "Access Range Summary" summarized I/O operation performance metrics for a separate, distinct "Access Range" associated with a specific "physical" device. An "Access Range" is an address span to which read and/or write I/O operations have performed data transfers as observed by the hIOmon I/O Monitor. BTW, the "Access Range Summary" metrics are based upon the "I/O Operation Trace" metrics that have been collected by hIOmon.

But that's another story.