File storage: Calculating available capacity and determining the placement of shares

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For each file-storage service class, IBM Spectrum Control calculates the amount of available capacity for NAS file shares of that service class. When you request file shares of a particular service class, IBM Spectrum Control recommends the best location for the shares from the available capacity.

Discontinued support: Cloud configuration, provisioning, and optimization are no longer supported in IBM Spectrum Control. While these features might still work in this release, it's recommended that you use another tool for your provisioning and optimization needs, when possible. For a complete list of discontinued features, see Discontinued features in IBM Spectrum Control.

For each file-storage service class, IBM Spectrum Control calculates the amount of available capacity for NAS file shares of that service class. When you request file shares of a particular service class, IBM Spectrum Control recommends the best location for the shares from the available capacity.

The Service Classes page displays the available capacity for each file-storage service class. The available capacity is the amount of space that is available across all IBM Storwize V7000 Unified file systems that are known to IBM Spectrum Control and that can satisfy the requirements of the service class. The set of file storage resources that are used to calculate the available capacity are also the candidates for provisioning by using the service class.

When you request a file share by using the Provision Storage pages, you specify the capacity that is required for the share, and you specify a service class. You can also specify a capacity pool from which shares must be provisioned. Based on the requested size of the share and whether a capacity pool is specified, the candidates for provisioning are further refined to include only the file storage resources that have enough available capacity and are in the specified capacity pool. From the remaining candidates for provisioning, IBM Spectrum Control creates a provisioning task that identifies the best location for the new share.

How available capacity for a file-storage service class is calculated

For each file-storage service class, IBM Spectrum Control calculates the available capacity for file shares of the service class. Only the file storage resources that are candidates for provisioning by using the service class are used to calculate the available capacity.

Identifying candidates for provisioning is a filtering process. File systems that could be candidates for provisioning if shared storage is allowed are eliminated as candidates for provisioning when dedicated storage is required. IBM Spectrum Control filters the set of available storage resources against each attribute of the service class until only the storage resources that can satisfy all of the requirements remain. These remaining storage resources are the candidates for provisioning.

The candidates for provisioning are identified by eliminating storage resources that cannot provide the service class, as follows:
  • Only IBM Storwize V7000 Unified systems are supported for provisioning file shares. No other storage system type is a candidate for provisioning file shares.
  • If a storage system has a consolidated status of Error or Unreachable, none of its internal NSDs or file systems are included in the available-space calculation.
  • If an NSD or file system has a consolidated status of Error, it is not included in the available-space calculation.
    Tip: The status of file systems is not displayed on the GUI. View the status on the NSD on which a file system resides to determine the file system status.
  • If the storage volume or NSD on which a file system resides has a consolidate status of Error, the file system is not included in the available-space calculation.
    Remember: Status is different from condition. Status is the status reported by a storage resource without considering the status of its internal resources. Condition is the combined status of the monitored, internal resources for the higher-level resource, and the status of the higher-level resource itself. The condition of a storage system is shown on the Storage Systems page, the condition of a volume is shown on the Volumes page, and the condition of an NSD is shown on the storage system details page. The condition might not have the same value as the status, which is used to eliminate file storage resources as candidates for provisioning.

    Although the condition of a resource might not have the same value as its status, the condition is always at least as severe as the status. The condition reflects the most severe status of any internal resource or the status of the resource itself. If the condition of a resource is Normal, then its status is also Normal.

    Tip: The Service Classes page displays both the available capacity and the unavailable capacity for a service class. The Unavailable Capacity column shows the amount of storage that satisfies the requirements of the service class, but is unavailable because of the consolidated status of the storage system or its internal resources.
  • If a service class allows provisioning only from certain capacity pools, any storage resource that is not in a specified capacity pool is eliminated as a candidate for provisioning.
    Tip: You can see whether a service class restricts provisioning to one or more capacity pools from the Service Classes page. On the Service Classes page, show the Capacity Pools column, which is hidden by default.
  • A file system or NSD must satisfy the requirements of every service class property in the following table to be a candidate for provisioning. Other properties of a service class are instructions for provisioning and do not affect the storage placement determination.
    Table 1. Filtering candidates for provisioning based on service class properties
    Service class attribute: Candidates for provisioning:
    Shared storage / Dedicated storage If the service class specifies dedicated storage, the share can be created only on an unused NSD. File systems and other file storage resources are eliminated as candidates for provisioning.
    Resource tags Resource tags further refine the candidates for provisioning. A service class can specify up to 3 resource tags. If resource tags are specified for the service class, only file systems and NSDs that have all the same tags are candidates for provisioning. If a file system or NSD is not tagged, any tags on the containing storage system also apply to the internal resource.

After the file storage resources that can provide the service class are identified, IBM Spectrum Control calculates the amount of space that is available for providing new files shares of the service class.

The available-space calculation differs depending on whether the file-storage service class requires dedicated storage or allows shared storage, as follows:
  • If the file-storage service class requires dedicated storage, the available capacity is the total available capacity on unused NSDs within each storage system. You can verify that an NSD is unused, and view its available capacity, from the details page of a storage system. To view information about the NSDs that are associated with a storage system, click Network Shared Disks. If the NSD is unused, the File Systems column shows 0. The Available Capacity column shows the amount of space on the NSD, which is the measurement that is used in the available-space calculation for the service class.
  • If the file-storage service class allows shared storage, the file system in which the NAS share is provisioned can contain other NAS shares. In this case the available capacity is the total of the following measurements:
    • The available capacity on unused NSDs within each storage system.
    • The available capacity for each file system within each IBM Storwize V7000 Unified storage system. You can view the file system available capacity from the details page of a file storage system. To view information about the file systems that are in a storage system, click File Systems. The Available Capacity column shows the amount of available capacity on each file system, which is the measurement that is used in the available-capacity calculation for the service class.

How the recommended placement of file shares is determined

When you request a file share by using the Provision Storage pages, the candidates for provisioning are further refined and a provisioning task is created which shows the recommended placement of the new share. The same filtering that was used to determine the available capacity for the service class is used, and is refined further as follows:
  • A provisioning request specifies the set of file storage resources from which the storage can be provisioned. This set can be all the storage resources that are known to IBM Spectrum Control, or can be limited to the storage resources in a particular capacity pool. Only the storage resources in the specified set are candidates for provisioning. This set might be more restrictive than the set used to calculate the available capacity for the service class.
  • Any storage resource that cannot provide the requested capacity for the share is eliminated as a candidate for provisioning.

The shares are created on file systems or NSDs. After the file systems and NSDs that can satisfy the provisioning request are identified, IBM Spectrum Control identifies the best location for the storage. The best location for the storage is based on the available capacity on the file system or NSD.