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Hitachi Vantara Knowledge

Understanding erasure coding topology details

The list of erasure coding topologies on the EC Topologies page shows the current status of each active, retiring, or retired erasure coding topology. To further monitor the status of a topology and to manage the topology, click the name of the topology in the list.

The page that opens shows details about the erasure coding topology in a Status section, HCP Systems section, and Overview panel, each of which is described below. The additional panels you can access on this page are:

  • Tenants panel

    Shows the tenants that are included in the topology and the tenants that are eligible to be included in the topology.

  • Settings panel

    Shows the erasure coding topology properties and lets you change those properties.

  • Management panel

    Lets you retire and delete the erasure coding topology.

Status section

The Status section on the details page for an erasure coding topology shows:

  • Topology state

    The current state of the topology. The topology state can be Active, Retiring, or Retired.

  • Protection status

    The current status of the erasure coding topology with respect to how well-protected erasure-coded objects are. The protection status can be:

    • Healthy

      All of these are true:

      • All systems in the topology are available.
      • The loss of a link in the topology would not cause any system to become unavailable.
      • The suspension of activity on a link in the topology would not prevent any system from receiving data or chunks for newly ingested objects.

      Data or chunks for newly ingested objects are being distributed to all systems in the topology. Full copies of object data will be reduced to chunks when the applicable erasure coding delay expires.

      Objects that were erasure coded according to the topology are protected.

    • Vulnerable

      One or both of these are true:

      • The loss of a link in the topology would cause a system in the topology to become unavailable.
      • The suspension of activity on a link in the topology would prevent a system in the topology from receiving data or chunks for newly ingested objects.

      Data or chunks for newly ingested objects are being distributed to all systems in the topology. Full copies of object data will be reduced to chunks when the applicable erasure coding delay expires.

      Objects that were erasure coded according to the topology are protected.

    • Broken

      One or more systems in the topology are unavailable.

      Data or chunks for newly ingested objects are being distributed to the systems that are available to the ingest system. However, full copies of object data won't be reduced to chunks until all systems in the topology are available, regardless of the erasure coding delay.

      Objects that were erasure coded according to the topology are not protected and may not be available.

    • Retiring

      Both of these are true:

      • The topology is in the process of retiring.
      • One or more systems in the topology still have chunks for objects that were erasure coded according to the topology.
    • Retired

      Both of these are true:

      • The topology has finished retiring.
      • No systems in the topology have chunks for objects that were erasure coded according to the topology.
    • Unknown

      HCP cannot determine the protection status.

  • Read status

    The current status of the erasure coding topology with respect to the ability to read erasure-coded objects.

    NoteFor the purpose of determining read status, HCP treats suspended links as broken links. However, if a suspended link is not actually broken, the systems involved in the link can still use the link to read data from each other.

    The read status can be:

    • Healthy

      Both of these are true:

      • The loss of a link in the topology would not cause the inability to read erasure-coded objects.
      • A system in the topology becoming unavailable would not cause the inability to read erasure-coded objects.

      The data for objects that were erasure coded according to the topology can be reconstructed or restored as needed.

    • Vulnerable

      All of these are true:

      • The data for objects that were erasure coded according to the topology can be reconstructed or restored as needed.
      • The loss of a link in the topology would cause the inability to read erasure-coded objects.
      • A system in the topology becoming unavailable would cause the inability to read erasure-coded objects.
    • Broken

      Two or more systems in the topology are unavailable. The data for objects that were erasure coded according to the topology cannot be reconstructed or restored unless the unavailability of all or all but one of those systems is due to links with suspended send activity.

    • Retired

      The topology has finished retiring. No systems in the topology have chunks for objects that were erasure coded according to the topology.

    • Unknown

      HCP cannot determine the read status.

  • Protection level

    x+y, where x is the number of data chunks and y is the number of parity chunks for each object that was erasure coded according to the topology.

  • Erasure-coded objects and object parts on this system

    The number of erasure-coded objects and erasure-coded parts of multipart objects on the current HCP system that were erasure coded according to the topology. An object or part is counted as erasure coded if a chunk for it is stored on the system.

    Parts of multipart objects are erasure coded independently of each other.

HCP Systems section

The HCP Systems section on the details page for an erasure coding topology contains a diagram of the topology and a numbered list of the systems in the topology.

The lines between the numbered systems in the topology diagram represent the replication links in the topology. The color of each line indicates the last known status of the applicable link:

  • Gray means healthy.
  • Orange means not replicating.
  • Red means unhealthy.
Overview panel

The Overview panel on the details page for an erasure coding topology contains a list of the replication links in the topology. For each link, the section shows:

  • Name

    The link name.

  • HCP System, HCP System

    The HCP systems involved in the link.

  • Status

    The last known status of the link. This status indicates the general health of the link. If the link is not directly connected to the current HCP system, the link status may be out of date.

    The link status can be:

    • Healthy

      The status displayed when the specific status of the link is one of these:

      • Synchronizing data
      • Scheduled off period
    • Not replicating

      The status displayed when the specific status of the link is one of these:

      • Suspended by user
      • Remote storage full, link suspended
      • Local storage full, link suspended
      • Failed over
    • Unhealthy

      The status displayed when the specific status of the link is one of these:

      • High error rate
      • Stalled link
      • Unrecognized link
      • Broken link
    • Unknown

      HCP cannot determine the specific status of the link.

  • Alerts

    If issues exist with the link, one or both of these icons:

    • GUID-BF1F61D2-3959-4DC1-A62B-C5939398AA1D-low.png

      This icon is displayed while replication is paused for one or more tenants on the link.

    • GUID-499EFF34-B983-4823-BFE5-90328E4CF16B-low.png

      This icon is displayed under these conditions:

      • One or more tenants added to the erasure coding topology have not been added to the link. HCP does not report this condition for a tenant until ten minutes after the tenant was added to the topology.

        This condition is reported only on the systems involved in the link.

      • HCP cannot find the link.

        This condition is reported only on the system where HCP cannot find the link. A link that cannot be found on one of the systems involved in the link is typically reported as broken on the other system involved in the link.

    To view text describing the condition that's causing the alert, hover over the alert icon.

 

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