• Overview

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    Overview

    Unity NFS support

    All Unity releases support NFSv3 and NFSv4. Unity also support secure NFS with Kerberos, for strong authentication. While Unity supports the majority of the NFSv4 and v4.1 functionality described in the relevant RFCs, directory delegation and pNFS are not supported.

    NFS support is enabled on a NAS server during or after creation, allowing you to create NFS-enabled file systems on that NAS server.

    Unisphere storage provisioning

    Storage provisioning is the process of allocating available drive capacity to meet the capacity, performance, and availability requirements of hosts and applications. When you provision storage with Unisphere, you create storage resources to which hosts and applications can connect in order to access storage.

    When you provision a storage resource in Unisphere, the system uses thin provisioning by default. This type of provisioning can improve storage efficiency while reducing the time and effort required for monitoring and rebalancing existing pool resources. Organizations can purchase less storage capacity up front, and increase available drive capacity (by adding drives) on an on-demand basis, and according to actual storage usage, instead of basing drive requirements in the requests or predictions of connected hosts. Thin provisioning allows multiple storage resources to subscribe to common storage capacity within a pool, while the system allocates only a portion of the physical capacity requested by each storage resource. The remaining storage is available for other storage resources to use.

    Note:  All storage resources require some amount of metadata from the pools where the storage resources were provisioned.
    Thick and thin provisioning

    The following table describes the differences between thick and thin provisioning:

    Table 1. Differences between thick and thin provisioning
    Provisioning type
    Description
    Thick provisioning
    The amount of storage requested for a storage resource is exclusively allocated for it. This storage is reserved, and the unused portion cannot be used or distributed among other storage resources associated with the same pool.
    Thin provisioning
    The amount of storage requested for a storage resource is not immediately allocated for it. Instead, the system allocates an initial quantity of storage to the storage resource. When the amount of storage consumed within the storage resource approaches the limit of the current allocation, the system allocates additional storage to the storage resource from the pool.

    Thin provisioning is required for data reduction.

    Figure 1. Difference between thick and thin provisioning

    An image that highlights the difference between standard provisioning and thin provisioning.

    Creating a thin storage resource

    When you create a thin storage resource, you specify a target size for the resource. The size represents the maximum capacity to which the storage resource can grow without being increased by an administrator. The system reserves only a portion of the requested size, called the initial allocation. The requested size of the storage resource represents a subscribed quantity. Additional storage is allocated on-demand.

    When a host or application uses approximately 75% of its initial allocation, an additional incremental quantity of storage is automatically allocated to the storage resource. The incremental allocation process continues until the quantity of storage allocated for the storage resource reaches the limit determined by its target size.

    Note:  A storage resource may appear full when data copied or written to the storage resource is greater than the space available at that time. When this occurs, the system begins to automatically extend the storage space and accommodate the write operation. As long as there is enough extension space available, this operation will complete successfully.
    Pool subscription levels

    Because storage resources can subscribe to more storage than is actually available to them, pools can be over-provisioned to support more storage capacity than they actually possess. The system automatically generates notification messages when total pool usage reaches 85% of the pool's physical capacity. (You can customize this threshold.)

    Thin provisioning best practices

    The following general rules can help determine the best environments in which to use thin provisioning:

    • Thin provisioning provides the benefit of space efficiency. It is recommended that you choose thin provisioning for a storage resource (selected by default), unless absolute and predictable performance is a higher requirement than space efficiency. In some workload environments, performance can actually improve with thin provisioning.
    • Environments that can benefit from thin provisioning include:
      • Document repositories with rapidly rising capacity requirements. These repositories can benefit greatly from the improved capacity utilization offered by thin provisioning, provided their environments meet the previously outlined criteria.
      • Software development and source code repositories. These repositories are well-suited to thin provisioning, because their environments can usually tolerate some level of performance variability.
    • Thin provisioning works best in file system environments where files are not frequently deleted. Many file systems do not efficiently reuse the space associated with deleted files, which can result in an allocated but unused space in the thin-provisioned file system.
    • Consider the space consumption characteristics of databases before using thin provisioning. Some databases pre-allocate the storage space for data before writing to it. This space is allocated within a thin-provisioned storage resource, and this can reduce the capacity utilization within the pool. For more information, consult your database vendor documentation.
    Advantages of thin and standard provisioning

    Thin provisioning provides the following advantages:

    • Provides the most efficient allocation of storage capacity based on usage.
    • Promotes ease of use in setting up and managing pool capacity.
    • Minimizes the host impact of adding pool resources based on host storage usage.
    • Optimizes storage usage in situations where space consumption is difficult to forecast.

    Planning considerations

    The following table summarizes the tasks to perform before you start configuring NFS on your Unity system. For more information on performing these tasks, see the Unity online help.

    1. Optionally configure at least one NTP server on the storage system to synchronize the date and time. It is recommended that you set up a minimum of two NTP servers per domain to avoid a single point of failure. This step is mandatory if you are using secure NFS.
    2. Optionally configure VLANs and tenants if you plan to implement multi-tenancy.
    3. Optionally configure a Unix Directory Service. This step is mandatory if you are using secure NFS, unless you use local files.
    4. Optionally configure one or more DNS servers. This step is mandatory if you are using secure NFS.

    Related features and functionality information

    Specific information related to the features and functionality described in this document is included in the following for Unity:

    • Unisphere Online Help
    • Configuring Hosts to Access NFS File Systems
    • Configuring Replication
    • Unisphere Command Line Interface User Guide
    • Service Commands Technical Notes

    The complete set of customer publications is available on the Online Support website at http://Support.EMC.com. After logging in to the website, click the Support by Product page and specify Dell EMC Unity Family to locate information for the specific feature required.