What are the use cases for a hard disk’s WWN?

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I noticed today while setting up a new system that the disk as represented by /dev/disk/by-id also had a WWN link that I was not familiar with:

enter image description here

My research suggests that this is a “World Wide Number” or some kind of unique ID to the drive. What is the use case for this and when would it be appropriate to use it versus the drive’s other represented ID, serial number, and UUID (from /dev/disk/by-uuid).

Links to documentation for this WWN identifier would also be useful. I’m getting a lot of hits on fiber channel stuff on Google. Is this a related use case or something else entirely?

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  • The WWN identifies the actual physical hardware disk. (Except when it doesn’t; a WWN can also identify storage which is not a hardware disk, for example a volume presented by a storage array.) UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).
    – AlexP
    Nov 27 at 19:53

up vote
0
down vote

favorite

I noticed today while setting up a new system that the disk as represented by /dev/disk/by-id also had a WWN link that I was not familiar with:

enter image description here

My research suggests that this is a “World Wide Number” or some kind of unique ID to the drive. What is the use case for this and when would it be appropriate to use it versus the drive’s other represented ID, serial number, and UUID (from /dev/disk/by-uuid).

Links to documentation for this WWN identifier would also be useful. I’m getting a lot of hits on fiber channel stuff on Google. Is this a related use case or something else entirely?

share|improve this question

  • The WWN identifies the actual physical hardware disk. (Except when it doesn’t; a WWN can also identify storage which is not a hardware disk, for example a volume presented by a storage array.) UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).
    – AlexP
    Nov 27 at 19:53

up vote
0
down vote

favorite

up vote
0
down vote

favorite

I noticed today while setting up a new system that the disk as represented by /dev/disk/by-id also had a WWN link that I was not familiar with:

enter image description here

My research suggests that this is a “World Wide Number” or some kind of unique ID to the drive. What is the use case for this and when would it be appropriate to use it versus the drive’s other represented ID, serial number, and UUID (from /dev/disk/by-uuid).

Links to documentation for this WWN identifier would also be useful. I’m getting a lot of hits on fiber channel stuff on Google. Is this a related use case or something else entirely?

share|improve this question

I noticed today while setting up a new system that the disk as represented by /dev/disk/by-id also had a WWN link that I was not familiar with:

enter image description here

My research suggests that this is a “World Wide Number” or some kind of unique ID to the drive. What is the use case for this and when would it be appropriate to use it versus the drive’s other represented ID, serial number, and UUID (from /dev/disk/by-uuid).

Links to documentation for this WWN identifier would also be useful. I’m getting a lot of hits on fiber channel stuff on Google. Is this a related use case or something else entirely?

disk uuid

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asked Nov 27 at 19:46

Zhro

344313

344313

  • The WWN identifies the actual physical hardware disk. (Except when it doesn’t; a WWN can also identify storage which is not a hardware disk, for example a volume presented by a storage array.) UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).
    – AlexP
    Nov 27 at 19:53

  • The WWN identifies the actual physical hardware disk. (Except when it doesn’t; a WWN can also identify storage which is not a hardware disk, for example a volume presented by a storage array.) UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).
    – AlexP
    Nov 27 at 19:53

The WWN identifies the actual physical hardware disk. (Except when it doesn’t; a WWN can also identify storage which is not a hardware disk, for example a volume presented by a storage array.) UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).
– AlexP
Nov 27 at 19:53

The WWN identifies the actual physical hardware disk. (Except when it doesn’t; a WWN can also identify storage which is not a hardware disk, for example a volume presented by a storage array.) UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).
– AlexP
Nov 27 at 19:53

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  • The WWN identifies the actual physical hardware disk; in simple cases it is derived from the hardware serial number. (Except when it doesn’t; a WWN can also identify storage which is not an actual hardware disk, it just pretends that it is for the sake of the operating system, for example, a volume presented by a storage array.)

  • UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).

[Storage arrays, for example a HPE 3PAR, are indeed usually connected to the computers which use them on a Fibre Channel Storage Area Network aka SAN. Infrastructure administrators configure the storage arrays to present logical disks to the hosts; each such logical disk is identified by a WWN.]

So the use cases when a WWN is appropriate are those when the administrator is interested in monitoring or configuring the actual physical (or, in the case of logical disks presented by storage array, the pseudo-physical) disk; for example, before any partition table or LVM metadata is written to the disk, the only honest identifier is the WWN. On the other hand, UUIDs can be copied from one physical disk to another, for example in order to perform a hardware upgrade.

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    • The WWN identifies the actual physical hardware disk; in simple cases it is derived from the hardware serial number. (Except when it doesn’t; a WWN can also identify storage which is not an actual hardware disk, it just pretends that it is for the sake of the operating system, for example, a volume presented by a storage array.)

    • UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).

    [Storage arrays, for example a HPE 3PAR, are indeed usually connected to the computers which use them on a Fibre Channel Storage Area Network aka SAN. Infrastructure administrators configure the storage arrays to present logical disks to the hosts; each such logical disk is identified by a WWN.]

    So the use cases when a WWN is appropriate are those when the administrator is interested in monitoring or configuring the actual physical (or, in the case of logical disks presented by storage array, the pseudo-physical) disk; for example, before any partition table or LVM metadata is written to the disk, the only honest identifier is the WWN. On the other hand, UUIDs can be copied from one physical disk to another, for example in order to perform a hardware upgrade.

    share|improve this answer

      up vote
      0
      down vote

      accepted

      • The WWN identifies the actual physical hardware disk; in simple cases it is derived from the hardware serial number. (Except when it doesn’t; a WWN can also identify storage which is not an actual hardware disk, it just pretends that it is for the sake of the operating system, for example, a volume presented by a storage array.)

      • UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).

      [Storage arrays, for example a HPE 3PAR, are indeed usually connected to the computers which use them on a Fibre Channel Storage Area Network aka SAN. Infrastructure administrators configure the storage arrays to present logical disks to the hosts; each such logical disk is identified by a WWN.]

      So the use cases when a WWN is appropriate are those when the administrator is interested in monitoring or configuring the actual physical (or, in the case of logical disks presented by storage array, the pseudo-physical) disk; for example, before any partition table or LVM metadata is written to the disk, the only honest identifier is the WWN. On the other hand, UUIDs can be copied from one physical disk to another, for example in order to perform a hardware upgrade.

      share|improve this answer

        up vote
        0
        down vote

        accepted

        up vote
        0
        down vote

        accepted

        • The WWN identifies the actual physical hardware disk; in simple cases it is derived from the hardware serial number. (Except when it doesn’t; a WWN can also identify storage which is not an actual hardware disk, it just pretends that it is for the sake of the operating system, for example, a volume presented by a storage array.)

        • UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).

        [Storage arrays, for example a HPE 3PAR, are indeed usually connected to the computers which use them on a Fibre Channel Storage Area Network aka SAN. Infrastructure administrators configure the storage arrays to present logical disks to the hosts; each such logical disk is identified by a WWN.]

        So the use cases when a WWN is appropriate are those when the administrator is interested in monitoring or configuring the actual physical (or, in the case of logical disks presented by storage array, the pseudo-physical) disk; for example, before any partition table or LVM metadata is written to the disk, the only honest identifier is the WWN. On the other hand, UUIDs can be copied from one physical disk to another, for example in order to perform a hardware upgrade.

        share|improve this answer

        • The WWN identifies the actual physical hardware disk; in simple cases it is derived from the hardware serial number. (Except when it doesn’t; a WWN can also identify storage which is not an actual hardware disk, it just pretends that it is for the sake of the operating system, for example, a volume presented by a storage array.)

        • UUIDs etc. identify logical structures (partitions, logical volumes, filesystems).

        [Storage arrays, for example a HPE 3PAR, are indeed usually connected to the computers which use them on a Fibre Channel Storage Area Network aka SAN. Infrastructure administrators configure the storage arrays to present logical disks to the hosts; each such logical disk is identified by a WWN.]

        So the use cases when a WWN is appropriate are those when the administrator is interested in monitoring or configuring the actual physical (or, in the case of logical disks presented by storage array, the pseudo-physical) disk; for example, before any partition table or LVM metadata is written to the disk, the only honest identifier is the WWN. On the other hand, UUIDs can be copied from one physical disk to another, for example in order to perform a hardware upgrade.

        share|improve this answer

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        answered Nov 27 at 19:57

        AlexP

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