Aligning partitions (and hence file system structures) to higher level
then 512 byte sectors is common practise and highly recommended for flash
backed block devices. It makes sure that the underlaying flash translation
layer (FTL) does not amplify writes due to missalignment of its erase
block size. Use a 1MiB boundary which is what a modern fdisk is doing.
Before this change:
# fdisk /dev/mmcblk0
Welcome to fdisk (util-linux 2.35.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): p
Disk /dev/mmcblk0: 14.57 GiB, 15634268160 bytes, 30535680 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
Disklabel type: dos
Disk identifier: 0x48617373
Device Boot Start End Sectors Size Id Type
/dev/mmcblk0p1 * 16384 65537 49154 24M c W95 FAT32 (LBA)
/dev/mmcblk0p2 65539 1228814 1163276 568M 5 Extended
/dev/mmcblk0p3 1228816 1425425 196610 96M 83 Linux
/dev/mmcblk0p4 1425427 30535679 29110253 13.9G 83 Linux
/dev/mmcblk0p5 65540 114693 49154 24M 83 Linux
/dev/mmcblk0p6 114695 638984 524290 256M 83 Linux
/dev/mmcblk0p7 638986 688139 49154 24M 83 Linux
/dev/mmcblk0p8 688141 1212430 524290 256M 83 Linux
/dev/mmcblk0p9 1212432 1228814 16383 8M 83 Linux
After this change:
# fdisk /dev/mmcblk0
Welcome to fdisk (util-linux 2.35.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): p
Disk /dev/mmcblk0: 14.57 GiB, 15634268160 bytes, 30535680 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
Disklabel type: dos
Disk identifier: 0x48617373
Device Boot Start End Sectors Size Id Type
/dev/mmcblk0p1 * 16384 65535 49152 24M c W95 FAT32 (LBA)
/dev/mmcblk0p2 65536 1239039 1173504 573M 5 Extended
/dev/mmcblk0p3 1241088 1437695 196608 96M 83 Linux
/dev/mmcblk0p4 1439744 30535679 29095936 13.9G 83 Linux
/dev/mmcblk0p5 67584 116735 49152 24M 83 Linux
/dev/mmcblk0p6 118784 643071 524288 256M 83 Linux
/dev/mmcblk0p7 645120 694271 49152 24M 83 Linux
/dev/mmcblk0p8 696320 1220607 524288 256M 83 Linux
/dev/mmcblk0p9 1222656 1239039 16384 8M 83 Linux
See also:
https://unix.stackexchange.com/questions/248939/how-to-achieve-optimal-alignment-for-emmc-partitionhttp://3gfp.com/wp/2014/07/formatting-sd-cards-for-speed-and-lifetime/
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