512 Bytes
If you are running linux then run the following command to get the detail -
$ fdisk -l // You require root privilege
Disk /dev/xvda: 8589 MB, ********** bytes, 16777216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes // This is what u are looking for
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: gpt
# Start End Size Type Name
1 4096 16777182 8G Linux filesyste Linux
128 2048 4095 1M BIOS boot parti BIOS Boot Partition