fat-cluster-chain · shipping · also File Allocation Table cluster chain

FAT cluster chain

A FAT cluster chain represents an allocation as an ordered sequence of cluster links ending in an end-of-chain marker.

Related Observatory article: FAT cluster chain on hesela.com

In Linux v6.12's exFAT code, chain traversal follows each FAT entry to the next cluster. A separate helper can create links between consecutive clusters, so the existence of a chain does not establish fragmentation. [1]

A synthetic ordering example: 20, 21, 22 and 20, 22, 21 occupy the same cluster set but order the file differently. Counting consecutive forward runs yields one and three, respectively. These are volume-cluster runs, not physical NAND locations or device-request counts.

Relations

related
exFAT, Allocation bitmap, Filesystem aging, Free-space fragmentation

Citations

  1. Linux v6.12: exFAT chain traversal and allocation, fs/exfat/fatent.c (accessed 2026-10-20)
Sources & caveats
  • The numeric sequences illustrate ordering only; they are not a complete volume image, measured workload or Linux allocator trace.

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Hesela team. FAT cluster chain. Hesela. 2026-10-20. https://hesela.dev/terms/fat-cluster-chain/