Tier

Tier is collection of physical disk that have similar performance characteristics.

About this task

Data isolation is an important requirement for segregating storage based on the workloads. Grouping of physical volumes having similar characteristics is critical to provide data isolation. Virtual I/O Server (VIOS) allows data isolation for shared storage pool by grouping the physical disks of a tier. There can be multiple tiers in the same shared storage pool thus providing data isolation based on the requirement of workload.

The other requirement is data mirroring. If applications use logical units from the shared storage pool in a data critical system need data mirroring. This can be achieved by enabling the failure group at the tier level. The VIOS allows physical disks to be associated with a failure group and assign it to a tier. So, you can mirror only the data that is critical.

The major attributes in Tier are :
  • Name : User defined name for tier.
  • UniqueDeviceID : VIOS generated ID for tier.
  • Type : Specifies it tier is System or User tier.
  • IsDefault : Specifies if tier is a default tier.
  • Capacity : Total capacity of Tier in GB.
  • FreeSpace : Total free space left out in Tier in GB.
  • OverCommitSpace : Amount of space over-committed by the tier to provide thin provisioning.
  • FreeSpaceThreshold : Specifies alert set on total percentage of frees pace available in tier.
  • OverCommitSpaceThreshold : Specifies alert set on total percentage of space over-commited by tier.
  • TotalLogicalUnitSize : Total size of logical units created under tier
  • MirrorState : Specifies if mirrioring is enabled on tier
  • FailureGroups : Collection of failgure configured for tier
  • FailureGroup Name: Specifies the user defined name of failure group
  • FailureGroup UniqueDeviceID: VIOS generated ID for tier.
  • FailureGroup Capacity : Total capacity of FailureGroup in GB.
  • FailureGroup State : Specifies the state of failure group
  • PhysicalVolumes : Collection of Physical Volume that are part of Shared storage pool.
  • AssociatedLogicalUnits : Collection of Logical units that are carved out of tier.
  • AssociatedSharedStoragePool : Specifies the Shared storage pool to which tier belong
Resource 
/rest/api/uom/Tier

This API provides information about the tiers that are a part of the shared storage pool managed by the hardware management console (HMC).

/rest/api/uom/Tier/{Tier_uuid}

This API provides information about a particular tier given its UUID.

/rest/api/uom/SharedStoragePool/SharedStoragePool_uuid/Tier

This API provides information about the tiers that are a part of the specified shared storage pool.

/rest/api/uom/SharedStoragePool/SharedStoragePool_uuid/Tier/{Tier_uuid}

This API provides information about a particular tier given its UUID, which is present in the specified shared storage pool.

Ignore error or Partial response

This option ignores the error generated from bad clusters and populates the tier information from the healthy clusters by populating partialresponseexception attribute at the feed level.

Resource 
/rest/api/uom/Tier?ignoreError=true

This option ignores the error from bad clusters and populates the tier information from the other healthy clusters by populating the partialresponseexception attribute at feed level.

/rest/api/uom/SharedStoragePool/SharedStoragePool_uuid/Tier?ignoreError=true

This option ignores the error from the bad clusters and populates the tier information only from the specified healthy cluster by populating the partialresponseexception attribute at feed level.

Quick properties

You can fetch the only the specified property.

Resource 
/rest/api/uom/Tier/{Tier_uuid}/quick/{Property name}

Supported property names are available at /rest/api/uom/Tier/quick URI.

Table 1. Quick properties
Quick property Description
Type The tier type as an enumeration key. For example, RestrictedSystemTier, UnrestrictedSystemTier, UserTier, or Unknown).
Capacity The capacity of the tier.
UniqueDeviceId The unique device ID of the Tier.
MirrorState The tier MirrorState as an enumeration key. For example, AIX_LINUX or OS_400.
Name The name of the tier.
Extended groups

Some attribute make calls to the underlying layer to get the data. These attributes are not cached and populated in REST API unless you specifically requested for them.

Resource 
/rest/api/uom/Tier?group={Group Name}

This API provides the tier information about the specified extended group attributes.

/rest/api/uom/Tier/{Tier_uuid}?group={Group Name}

This API provides information about the specified extended group attributes of the given tier instance.

/rest/api/uom/SharedStoragePool/{SharedStoragePool_uuid}/Tier?group={Group Name}

This API provides information about the specified extended group attributes of the given instance.

/rest/api/uom/SharedStoragePool/{SharedStoragePool_uuid}/Tier/{Tier_uuid}?group={Group Name}

This API provides information about the specified extended group attributes of the given instance.

Table 2. List of extended groups
Group name Description
Advanced This extended group call populates FreeSpace, OverCommitSpace, and TotalLogicalUnitSize value of a tier.
TierThreshold This extended group call populates FreeSpaceThreshold and OverCommitSpaceThreshold value of a tier.
None This is an extended group that provides the default attributes.
Table 3. Supported methods
Method Description Internet media type
GET Fetch the tier information from all managed VIOS. application/atom+xml, application/vnd.ibm.powervm.uom+xml; type=Tier
PUT Create a new tier in a specified Shared storage pool. application/atom+xml, application/vnd.ibm.powervm.uom+xml; type=Tier
POST Update the existing tier. You can do any of the following actions:
  • Modify tier name.
  • Modify tier type.
  • Set tier as default tier.
  • Modify FreeSpaceThreshold of Tier.
  • Modify OverCommitSpaceThreshold of Tier.
  • Add new failure group to Tier.
  • Modify failure group name in a Tier.
  • Add Physcial Volumes to failure group.
  • Remove Physical Volumes from failure group.
  • Replace Physical Volumes in failure group.
  • Remove failure group from a Tier.
 application/atom+xml, application/vnd.ibm.powervm.uom+xml; type=Tier
DELETE Delete the specified tier. application/atom+xml, application/vnd.ibm.powervm.uom+xml; type=Tier
Note :

There exists a default tier of SYSTEM type which gets created when cluster is created without specifying multiple tier.

Since: Version 1_3_0