Considerations for which start sector to use for a data partition on uSD media

Installing and Using OpenWrt
1

I recently found a need to increase my rootfs size from 104 MiB to 256 MiB. I want to create a data partition on the rest of the uSD card. Is there any rule about which start sector to use? Should they be divisible by some number for example or does it simply not matter.

I ask because I noticed that the default image created sdd1 and sdd2 and did so leaving 8,193 sectors of blank space between them. (147456 - 139263 = 8193).

Disk /dev/sdd: 14.84 GiB, 15931539456 bytes, 31116288 sectors
Disk model: STORAGE DEVICE  
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: 0x5452574f

Device     Boot  Start      End  Sectors  Size Id Type
/dev/sdd1  *      8192   139263   131072   64M  c W95 FAT32 (LBA)
/dev/sdd2       147456   671743   524288  256M 83 Linux

I took that same number to use a buffer adding it to the next available one for my third partition:

Device     Boot  Start      End  Sectors  Size Id Type
/dev/sdd1  *      8192   139263   131072   64M  c W95 FAT32 (LBA)
/dev/sdd2       147456   671743   524288  256M 83 Linux
/dev/sdd3       679936 31116287 30436352 14.5G 83 Linux
2

Generally fdisk/ gdisk/ parted tend to do the right thing (unless you dive deep into the semi-hidden advanced options).

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