Hi,
I'm having troubles at the first step: determining the erase block size. The strange results are below. The original FAT layout was not saved when the drive was purchased.
# lsusb Bus 004 Device 002: ID 125f:c82a A-DATA Technology Co., Ltd.
# fdisk -l /dev/disk/by-id/usb-ADATA_USB_Flash_Drive_1061309422330015-0:0
Disk /dev/disk/by-id/usb-ADATA_USB_Flash_Drive_1061309422330015-0:0: 7873 MB, 7873757184 bytes 180 heads, 14 sectors/track, 6102 cylinders, total 15378432 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: 0xf65985aa
Device Boot Start End Blocks Id System /dev/disk/by-id/usb-ADATA_USB_Flash_Drive_1061309422330015-0:0-part1 2048 15378431 7688192 83 Linux
# for i in 1 2 4 8 16; do echo -e "\n\nbs=$[$i*1024]"; flashbench -a /dev/disk/by-id/usb-ADATA_USB_Flash_Drive_1061309422330015-0:0 --blocksize=$[$i*1024]; done
bs=1024 align 2147483648 pre 829µs on 815µs post 836µs diff -17473n align 1073741824 pre 846µs on 796µs post 853µs diff -53379n align 536870912 pre 744µs on 781µs post 834µs diff -8238ns align 268435456 pre 827µs on 798µs post 831µs diff -31049n align 134217728 pre 758µs on 763µs post 763µs diff 2.71µs align 67108864 pre 789µs on 779µs post 815µs diff -22737n align 33554432 pre 773µs on 747µs post 779µs diff -29372n align 16777216 pre 695µs on 773µs post 816µs diff 16.8µs align 8388608 pre 688µs on 728µs post 691µs diff 39µs align 4194304 pre 733µs on 779µs post 815µs diff 4.47µs align 2097152 pre 742µs on 761µs post 759µs diff 10.8µs align 1048576 pre 811µs on 793µs post 817µs diff -21380n align 524288 pre 799µs on 794µs post 816µs diff -13187n align 262144 pre 756µs on 795µs post 800µs diff 17µs align 131072 pre 737µs on 685µs post 744µs diff -55710n align 65536 pre 741µs on 747µs post 747µs diff 3.18µs align 32768 pre 798µs on 780µs post 799µs diff -18178n align 16384 pre 732µs on 779µs post 796µs diff 15.1µs align 8192 pre 740µs on 776µs post 799µs diff 7.01µs align 4096 pre 952µs on 758µs post 799µs diff -117830 align 2048 pre 738µs on 774µs post 798µs diff 6.04µs
bs=2048 align 2147483648 pre 853µs on 848µs post 869µs diff -12804n align 1073741824 pre 861µs on 869µs post 869µs diff 3.88µs align 536870912 pre 833µs on 834µs post 835µs diff -193ns align 268435456 pre 877µs on 907µs post 900µs diff 18.4µs align 134217728 pre 842µs on 851µs post 870µs diff -5455ns align 67108864 pre 828µs on 799µs post 833µs diff -31688n align 33554432 pre 767µs on 827µs post 832µs diff 26.9µs align 16777216 pre 758µs on 776µs post 762µs diff 16.2µs align 8388608 pre 713µs on 714µs post 712µs diff 868ns align 4194304 pre 857µs on 887µs post 866µs diff 25.9µs align 2097152 pre 837µs on 867µs post 872µs diff 12.7µs align 1048576 pre 847µs on 834µs post 847µs diff -13895n align 524288 pre 865µs on 882µs post 866µs diff 16.4µs align 262144 pre 864µs on 849µs post 868µs diff -17470n align 131072 pre 795µs on 799µs post 799µs diff 1.98µs align 65536 pre 868µs on 868µs post 867µs diff 205ns align 32768 pre 866µs on 867µs post 868µs diff -623ns align 16384 pre 859µs on 853µs post 871µs diff -11754n align 8192 pre 859µs on 869µs post 849µs diff 15µs align 4096 pre 978µs on 980µs post 829µs diff 76.4µs
bs=4096 align 2147483648 pre 905µs on 908µs post 1.05ms diff -70516n align 1073741824 pre 997µs on 979µs post 1.11ms diff -72729n align 536870912 pre 961µs on 978µs post 1.1ms diff -51399n align 268435456 pre 965µs on 973µs post 1.07ms diff -42441n align 134217728 pre 890µs on 891µs post 1.03ms diff -70698n align 67108864 pre 855µs on 838µs post 1.02ms diff -97971n align 33554432 pre 853µs on 870µs post 1.05ms diff -80043n align 16777216 pre 832µs on 832µs post 1.03ms diff -98061n align 8388608 pre 842µs on 843µs post 1.03ms diff -92877n align 4194304 pre 933µs on 960µs post 1.08ms diff -46878n align 2097152 pre 924µs on 926µs post 1.03ms diff -51066n align 1048576 pre 948µs on 925µs post 1.07ms diff -82986n align 524288 pre 970µs on 981µs post 1.1ms diff -55840n align 262144 pre 985µs on 954µs post 1.12ms diff -97010n align 131072 pre 933µs on 944µs post 1.08ms diff -60718n align 65536 pre 970µs on 956µs post 1.03ms diff -46152n align 32768 pre 963µs on 943µs post 1.11ms diff -91246n align 16384 pre 914µs on 924µs post 1.07ms diff -67228n align 8192 pre 923µs on 924µs post 1.09ms diff -80328n
bs=8192 align 2147483648 pre 1.66ms on 1.62ms post 1.64ms diff -29621n align 1073741824 pre 1.65ms on 1.64ms post 1.68ms diff -22022n align 536870912 pre 1.62ms on 1.62ms post 1.62ms diff 662ns align 268435456 pre 1.62ms on 1.6ms post 1.62ms diff -17675n align 134217728 pre 1.64ms on 1.61ms post 1.64ms diff -31935n align 67108864 pre 1.68ms on 1.67ms post 1.67ms diff -3326ns align 33554432 pre 1.73ms on 1.74ms post 1.74ms diff 9.42µs align 16777216 pre 1.66ms on 1.64ms post 1.64ms diff -7797ns align 8388608 pre 1.65ms on 1.66ms post 1.65ms diff 8.27µs align 4194304 pre 1.63ms on 1.65ms post 1.65ms diff 10.3µs align 2097152 pre 1.62ms on 1.64ms post 1.64ms diff 6.62µs align 1048576 pre 1.66ms on 1.66ms post 1.65ms diff 2.68µs align 524288 pre 1.66ms on 1.64ms post 1.64ms diff -6934ns align 262144 pre 1.65ms on 1.66ms post 1.66ms diff 197ns align 131072 pre 1.64ms on 1.64ms post 1.64ms diff 1.64µs align 65536 pre 1.65ms on 1.62ms post 1.62ms diff -12165n align 32768 pre 1.66ms on 1.66ms post 1.67ms diff -9644ns align 16384 pre 1.62ms on 1.62ms post 1.64ms diff -9352ns
bs=16384 align 2147483648 pre 2.39ms on 2.35ms post 2.33ms diff -7216ns align 1073741824 pre 2.46ms on 2.44ms post 2.43ms diff 341ns align 536870912 pre 2.28ms on 2.28ms post 2.28ms diff -1850ns align 268435456 pre 2.32ms on 2.28ms post 2.3ms diff -29446n align 134217728 pre 2.3ms on 2.32ms post 2.32ms diff 7.53µs align 67108864 pre 2.32ms on 2.31ms post 2.3ms diff 2.12µs align 33554432 pre 2.38ms on 2.41ms post 2.43ms diff 4µs align 16777216 pre 2.32ms on 2.28ms post 2.27ms diff -7553ns align 8388608 pre 2.28ms on 2.28ms post 2.29ms diff -6386ns align 4194304 pre 2.28ms on 2.28ms post 2.28ms diff -1055ns align 2097152 pre 2.28ms on 2.26ms post 2.28ms diff -18798n align 1048576 pre 2.28ms on 2.28ms post 2.26ms diff 9.31µs align 524288 pre 2.33ms on 2.32ms post 2.32ms diff -4279ns align 262144 pre 2.29ms on 2.28ms post 2.25ms diff 8.77µs align 131072 pre 2.3ms on 2.26ms post 2.3ms diff -35064n align 65536 pre 2.31ms on 2.27ms post 2.28ms diff -33000n align 32768 pre 2.3ms on 2.31ms post 2.34ms diff -730ns
# flashbench -a /dev/disk/by-id/usb-ADATA_USB_Flash_Drive_1061309422330015-0:0 --blocksize=$[10*1024] align 1342177280 pre 1.66ms on 2.14ms post 1.69ms diff 465µs align 671088640 pre 1.66ms on 2.16ms post 1.66ms diff 499µs align 335544320 pre 1.69ms on 2.19ms post 1.71ms diff 493µs align 167772160 pre 1.76ms on 2.26ms post 1.75ms diff 510µs align 83886080 pre 1.62ms on 2.09ms post 1.67ms diff 447µs align 41943040 pre 1.8ms on 2.33ms post 1.76ms diff 551µs align 20971520 pre 1.62ms on 2.12ms post 1.64ms diff 490µs align 10485760 pre 1.64ms on 2.1ms post 1.65ms diff 455µs align 5242880 pre 1.62ms on 2.08ms post 1.68ms diff 432µs align 2621440 pre 1.65ms on 2.12ms post 1.68ms diff 456µs align 1310720 pre 1.6ms on 2.03ms post 1.55ms diff 450µs align 655360 pre 1.57ms on 2.03ms post 1.62ms diff 437µs align 327680 pre 1.66ms on 2.08ms post 1.64ms diff 435µs align 163840 pre 1.63ms on 2.06ms post 1.62ms diff 436µs align 81920 pre 1.64ms on 2.08ms post 1.64ms diff 447µs align 40960 pre 1.66ms on 2.19ms post 1.73ms diff 499µs align 20480 pre 2.07ms on 1.64ms post 1.66ms diff -226664