The block size is a platform-dependent value that is greater than or equal to the sector size. Each platform accesses the disk on block boundaries and in quantities that are multiples of the block size.
Data that is created on one platform, and then accessed by a platform of a different block size, can suffer from the following problems:
The size of the data written may not be an exact multiple of the block size used by the accessing platform. Therefore the accessing platform cannot constrain its I/O within the boundaries of the data on disk.