Amiga Rigid Disk Block

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In computing, a Rigid Disk Block is the block on a hard disk where the Amiga series of computers store the disk's partition and filesystem information. The PC equivalent of the Amiga's RDB is the Master Boot Record.

Unlike its PC equivalent, the RDB doesn't directly contains metadata for each partition. Instead it points to a linked list of partition blocks, which by itself contains the actual partition data, their start, length, filesystem, their boot priority, their buffer memory type and their "flavor" though the latter was never used. Because there is no limitation in partition block count, there is no need to distinguish primary and extended types and all partitions are equal in stature and architecture.

The Rigid Disk Block must start with the Bytes 52₁₆ 44₁₆ 53₁₆ 4B₁₆, which means "RDSK" in ASCII representation. Furthermore, its position isn't restricted to the very first block of a volume, instead it could be located anywhere within its first 16 blocks. Thus it could be safely coexist with a Master Boot Record, which is forced to be found at block 0.