On Sunday 02 September 2012, Jaroslav Martínek wrote:

Hi,

I'm trying to figure out parameters of my USB drive with Flashbench, but I'm a bit confused with the results.

# Product info:

http://www.adata-group.com/index.php?action=product_feature&cid=1&pi...

$ sudo fdisk -l /dev/sdb

Disk /dev/sdb: 31.2 GB, 31161974784 bytes 255 heads, 63 sectors/track, 3788 cylinders, total 60863232 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0007e2e8

$ sudo flashbench -a /dev/sdb --blocksize=1024 align 8589934592 pre 655µs on 744µs post 644µs diff 95.1µs align 4294967296 pre 654µs on 774µs post 657µs diff 118µs align 2147483648 pre 643µs on 804µs post 633µs diff 166µs align 1073741824 pre 538µs on 562µs post 528µs diff 28.2µs align 536870912 pre 582µs on 594µs post 562µs diff 21.7µs align 268435456 pre 576µs on 619µs post 565µs diff 48.3µs align 134217728 pre 579µs on 637µs post 561µs diff 66.5µs align 67108864 pre 563µs on 617µs post 567µs diff 51.8µs align 33554432 pre 537µs on 578µs post 522µs diff 48.2µs align 16777216 pre 552µs on 563µs post 512µs diff 30.5µs align 8388608 pre 647µs on 758µs post 646µs diff 111µs align 4194304 pre 631µs on 726µs post 616µs diff 102µs align 2097152 pre 629µs on 744µs post 630µs diff 115µs align 1048576 pre 633µs on 747µs post 623µs diff 119µs align 524288 pre 641µs on 751µs post 617µs diff 122µs align 262144 pre 636µs on 742µs post 623µs diff 112µs align 131072 pre 618µs on 752µs post 643µs diff 121µs align 65536 pre 604µs on 759µs post 634µs diff 140µs align 32768 pre 631µs on 741µs post 616µs diff 117µs align 16384 pre 644µs on 744µs post 624µs diff 111µs align 8192 pre 636µs on 679µs post 617µs diff 52µs align 4096 pre 614µs on 641µs post 628µs diff 20.3µs align 2048 pre 606µs on 629µs post 629µs diff 11.4µs

# Well, from what I've read so far the page size could be 8kB, but what about the erase block? This drive seems to behave quite differently than the example in readme or other cards in this list. Any ideas?

This very much looks like a 16MB erase block size and a 16KB page size. It is a bit unusual that the last column has lower values for the larger sizes (>=16MB) than for the ones below that, but the more important question is whether the numbers are /different/.

The '-a' test is just a help for guessing the erase size anyway, so doing the '--open-au' test you can start out with this 16MB value and see what you get out of it, then cross-check against other sizes like 8MB and 12MB.

Arnd