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As the arch install guide suggests (using parted to do the partitioning)
(parted) mkpart primary ext4 1MiB 100MiB
However, when checking the output of fdisk, the start of the partition is not the 1024 byte but 2048 byte. Afaik, the 1MiB is used there to prevent possible errors, for example, when creating the partition table which store info in the first byte.
What is the reason of not using something like this?
(parted) mkpart primary ext4 0MiB 100MiB
In the case of MBR (and 1/2 KiB blocks) the information are stored in the first block (first 512 bytes) and for historical reasons and out of compatibility with various OSes the first really useful block would be the 63th. The space in-between is often used by boot-loaders for the program code for one of their levels.
In the case of GPT you have the Protective MBR in the first block in order to mimic a MBR partition table (and one big partitions) for those tools that might not support it. Then comes the GPT header and GPT info until the 34th block, allowing for 128 GPT entries.
