nvme-namespace-identifiers · shipping · also NVMe NGUID, NVMe EUI64, NVMe namespace UUID

NVMe namespace identifiers

NVMe namespace identifiers are the NGUID, EUI64 and namespace UUID values used to distinguish a namespace independently of its command-addressing NSID.

NGUID is 128-bit and EUI64 is 64-bit; Identify Namespace reports both fields [1]. Namespace identification descriptors distinguish EUI64, NGUID and 128-bit UUID types [3]. These protocol identifiers are not filesystem UUIDs or partition GUIDs.

Linux v6.12 compares UUID, NGUID, EUI64 and the command-set identifier before accepting another path for a shared NSID in a subsystem [4]. This identity check is separate from deciding which path can serve I/O [5].

NGUID and EUI64 remain stable during the namespace lifetime, including controller reset and namespace format; zero means that field provides no identifier [1]. NSFEAT.UIDREUSE=0 permits nonzero NGUID/EUI64 reuse after deletion; UIDREUSE=1 prohibits it [2]. This rule does not describe UUID reuse.

For dispersed namespaces, NSIDs may differ between participating subsystems; the common identifier is NGUID or namespace UUID, not EUI64, with NGUID selected when both exist [6]. This does not establish support in a particular host implementation.

Relations

related

namespace-nvme, nvme-nsid, nvme-subsystem-nqn, multipath-nvme

Advantages

• Allows namespace recognition without relying only on an NSID or an operating-system device name.

Limitations

• Not all three forms must be populated.
• Duplicate or inconsistent identifiers require investigation, not forced path merging.

Citations

1. NVM Express NVM Command Set Specification 1.0c, Figure 97; copyright 2008-2022 NVM Express, Inc., all rights reserved (accessed 2026-10-16)
2. NVM Express Base Specification 2.0e, section 4.5.1; copyright 2008-2024 NVM Express, Inc., all rights reserved (accessed 2026-10-16)
3. libnvme upstream types: nvme_ns_id_desc and nvme_ns_id_desc_nidt (accessed 2026-10-16)
4. Linux v6.12 NVMe host core: nvme_ns_ids_equal and nvme_init_ns_head (accessed 2026-10-16)
5. NVMe multipath: ANA access states and Linux path policies (accessed 2026-10-16)
6. NVM Express Base Specification 2.3, section 8.1.10.2: dispersed namespace identity; copyright NVM Express, Inc. (accessed 2026-10-16)

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