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When I format an ext4 filesystem the mkfs says:

Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
4096000

My sparse_super flag is ON, so according to the ext4 description, the superblock copies should be stored in groups with numbers, which are powers of 3, 5 or 7. So, these groups will be 3, 5, 7, 9, 25, 27, 49, 81, 125 (from total 160 groups). Multiplying these numbers on 32768 (blocks per group) I get only last 9 values from the mkfs list above.

Why the first superblock copy is stored in the group #1? This number is not a power of 3, 5 or 7.

HEKTO
  • 145

1 Answers1

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The exponent counting is zero-based, so the first power of 3, 5 and 7 (or any other base for that matter) is actually 3^0, 5^0 and 7^0 which is 1. The first superblock copy is always in group 1.

oranav
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