deallocated-read-behavior · shipping · also Read after deallocation

Deallocated read behavior

The interface-defined data or error returned when a host reads a deallocated logical block.

In NVMe 1.4a, DLFEAT describes deallocated data values and DULBE controls the supported deallocated/unwritten-block error. This concerns the logical interface, not direct inspection of physical media.

Relations

related

discard, trim, scsi-unmap, nvme, data-sanitization

Limitations

• Linux discard_zeroes_data always returns zero and should not be used to infer readback semantics.

Citations

1. NVM Express 1.4a: sections 6.7, 6.7.1.1 and Figure 247 (accessed 2026-10-11)
2. Linux 6.12: stable sysfs block ABI, discard attributes (accessed 2026-10-11)
3. Hesela: Discard is not zeroing (accessed 2026-10-11)

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