This is the first Sandisk Card that I've seen that does not have any optimizations for random access. It's particularly bad since this card was specifically shipped with a Linux box for the purpose of installing Debian on it. The label says "15 MB/s read, 7 MB/s write".

Arnd ---

$ head /sys/block/mmcblk0/device/{c*,scr,*rev,*id,serial,*size} ==> /sys/block/mmcblk0/device/cid <== 035344534430324780019b8975009b00 ==> /sys/block/mmcblk0/device/csd <== 002600325f5a83aefefbcfff92804000 ==> /sys/block/mmcblk0/device/scr <== 0225000000000000 ==> /sys/block/mmcblk0/device/fwrev <== 0x0 ==> /sys/block/mmcblk0/device/hwrev <== 0x8 ==> /sys/block/mmcblk0/device/cid <== 035344534430324780019b8975009b00 ==> /sys/block/mmcblk0/device/manfid <== 0x000003 ==> /sys/block/mmcblk0/device/oemid <== 0x5344 ==> /sys/block/mmcblk0/device/serial <== 0x019b8975 ==> /sys/block/mmcblk0/device/erase_size <== 512 ==> /sys/block/mmcblk0/device/preferred_erase_size <== 4194304

$ sudo ./flashbench -a /dev/mmcblk0 --blocksize 1024 --count=50 align 268435456 pre 896µs on 1.14ms post 697µs diff 345µs align 134217728 pre 671µs on 983µs post 641µs diff 327µs align 67108864 pre 748µs on 1.02ms post 615µs diff 336µs align 33554432 pre 615µs on 699µs post 582µs diff 99.9µs align 16777216 pre 671µs on 807µs post 634µs diff 154µs align 8388608 pre 759µs on 822µs post 698µs diff 93.2µs align 4194304 pre 716µs on 822µs post 692µs diff 118µs align 2097152 pre 745µs on 824µs post 701µs diff 101µs align 1048576 pre 633µs on 662µs post 669µs diff 11.5µs align 524288 pre 636µs on 668µs post 656µs diff 22µs align 262144 pre 630µs on 673µs post 657µs diff 29.6µs align 131072 pre 629µs on 673µs post 661µs diff 28.4µs align 65536 pre 640µs on 670µs post 665µs diff 17.2µs align 32768 pre 629µs on 671µs post 667µs diff 23.1µs align 16384 pre 618µs on 664µs post 658µs diff 25.5µs align 8192 pre 643µs on 643µs post 637µs diff 3.5µs align 4096 pre 657µs on 661µs post 645µs diff 10.1µs align 2048 pre 661µs on 669µs post 656µs diff 10.8µs

$ sudo ./flashbench --open-au --open-au-nr=1 /dev/mmcblk0 --erasesize=$[2 * 1024 * 1024] --blocksize=1024 --random 2MiB 11.1M/s 1MiB 3.72M/s 512KiB 3.26M/s 256KiB 1.38M/s 128KiB 1.89M/s 64KiB 1.43M/s 32KiB 918K/s 16KiB 350K/s 8KiB 1.16M/s 4KiB 542K/s 2KiB 254K/s 1KiB 121K/s

sudo ./flashbench --open-au --open-au-nr=1 /dev/mmcblk0 --erasesize=$[2 * 1024 * 1024] --blocksize=1024 2MiB 6.91M/s 1MiB 6.1M/s 512KiB 6.06M/s 256KiB 6.11M/s 128KiB 6.39M/s 64KiB 12.1M/s 32KiB 9.97M/s 16KiB 6.74M/s 8KiB 3.66M/s 4KiB 2.04M/s 2KiB 945K/s 1KiB 461K/s

$ sudo ./flashbench --open-au --open-au-nr=6 /dev/mmcblk0 --erasesize=$[2 * 1024 * 1024] --blocksize=1024 --random 2MiB 11.5M/s 1MiB 10.1M/s 512KiB 7.91M/s 256KiB 3M/s 128KiB 2.2M/s 64KiB 1.21M/s 32KiB 645K/s 16KiB 310K/s 8KiB 176K/s 4KiB 86.8K/s ^C

$ sudo ./flashbench --open-au --open-au-nr=6 /dev/mmcblk0 --erasesize=$[2 * 1024 * 1024] --blocksize=1024 2MiB 9.79M/s 1MiB 11.7M/s 512KiB 11.9M/s 256KiB 11.8M/s 128KiB 11.7M/s 64KiB 11.8M/s 32KiB 9.77M/s 16KiB 6.64M/s 8KiB 4.13M/s 4KiB 2M/s 2KiB 929K/s 1KiB 445K/s

$ sudo ./flashbench --open-au --open-au-nr=7 /dev/mmcblk0 --erasesize=$[2 * 1024 * 1024] --blocksize=1024 --random 2MiB 12M/s 1MiB 6.1M/s 512KiB 3.23M/s 256KiB 1.55M/s 128KiB 772K/s 64KiB 384K/s 32KiB 192K/s 16KiB 95.8K/s 8KiB 47.7K/s ^C

$ sudo ./flashbench --open-au --open-au-nr=7 /dev/mmcblk0 --erasesize=$[2 * 1024 * 1024] --blocksize=1024 2MiB 11M/s 1MiB 7.75M/s 512KiB 3.2M/s 256KiB 1.54M/s 128KiB 768K/s 64KiB 384K/s ^C

$ sudo ./flashbench --findfat --fat-nr=4 /dev/mmcblk0 --blocksize=1024 --erasesize=$[2* 1024 * 1024] --random 2MiB 11.9M/s 12M/s 11.7M/s 12M/s 1MiB 5.54M/s 5.69M/s 5.11M/s 7.73M/s 512KiB 7.08M/s 4.65M/s 4.35M/s 4.35M/s 256KiB 6.98M/s 2.26M/s 2.27M/s 2.26M/s 128KiB 7.98M/s 5.47M/s 5.48M/s 5.47M/s 64KiB 8.4M/s 5.62M/s 5.57M/s 5.45M/s 32KiB 7.16M/s 4.89M/s 4.94M/s 4.83M/s 16KiB 5.3M/s 2.32M/s 2.32M/s 2.27M/s 8KiB 2.31M/s 2.33M/s 2.33M/s 2.33M/s 4KiB 943K/s 945K/s 942K/s 944K/s 2KiB 411K/s 408K/s 410K/s 410K/s 1KiB 190K/s 187K/s 192K/s 192K/s