I might have inadvertently led some folks to think based upon my prior posts #283 and #285 that AS SSD first performs its write testing followed by its read testing when only its "Access Time" option is selected.

My intent was to discuss write I/O operations first in post #283 (since that discussion seemed more straightforward) and then deal with the read I/O operations within the subsequent post #285.

Here is the actual sequence as observed by hIOmon:

Step 1:

26214 physical device random read I/O operations each with a data transfer length of 4096 for "\Device\Harddisk..." for a total data transferred read amount of 107 372 544 bytes

Step 2:

  1. 1 single read file I/O operation with a data transfer length of zero for the "AS-SSD-TEST42\test.bin" test file
  2. 64 write file I/O operations each with a data transfer length of 16 777 216 sequentially to "AS-SSD-TEST42\test.bin" for a total data transferred write amount of 1GiB
NOTE: These file write I/O operations are subject to "split I/O" operations due to file fragmentation; they can also subsequently be further decomposed into smaller write I/O operations with a data transfer size of 1 048 576 bytes (in this case) at the physical device level (with potential queuing implications).

Step 3:

  1. 1 single read file I/O operation with a data transfer length of zero for "AS-SSD-TEST42\test.bin"
  2. 1 single write file I/O operations with a data transfer length of 4096 for "AS-SSD-TEST42\test.bin"
  3. 26214 random write file I/O operations each with data transfer length of 512 bytes to "AS-SSD-TEST42\test.bin" for a total data transferred write amount of 13 421 568 bytes; each of these file write I/O operations results in a corresponding physical device write I/O operation with a data transfer length of 512 bytes. Also note that the combined amount of data written by this and (2) above is 13 425 664 bytes (and in comparison to the 107 372 544 bytes bytes read via the physical device read I/O operations in Step 1).

Finally, several (perhaps subtle) items for consideration (particularly in light of SSD flash management):
  1. The read I/O operations in Step 1 are to random locations upon the physical device; presumably these locations (blocks/sectors) may or may not have been written to previously

  2. Action 2 in Step 2 might be considered to be a "sequential pre-conditioning" of the test area for the subsequent write I/O operations (i.e., action 3 in Step 3)

  3. The 512B random write I/O operations performed in action 3 of Step 3 are presumably to stress the flash media management of the SSD (with potential wear-leveling implications), but to a limited amount of the overall area written by action 2 in Step 2