• Configuring LUNs and consistency groups

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    Configuring LUNs and consistency groups

    About LUN storage

    LUN storage resources provide hosts with access to general purpose block-level storage through network-based iSCSI or Fibre Channel (FC) connections. With LUN storage you can manage addressable partitions of block storage resources so that host systems can mount and use these resources (LUNs) over FC or IP connections. After a host connects to the LUN, it can use the LUN like a local storage drive.

    Figure 1. LUN storage overview
    An image illustrating the overview of iSCSI storage.

    Each interface has a unique VLAN ID (checked locally for the port) and an IP address (checked locally for the storage system) for iSCSI connections and a World Wide Name (WWN) for FC connections.

    Note:  Different physical network ports can have the same VLAN ID.

    The following table lists the components of LUN storage:

    Table 1. Components of LUN storage
    Component
    Description
    LUN
    A block of storage that can stand alone or may be associated with a consistency group. Allocated from a pool, you can use a LUN for one or more hosts. A LUN represents a quantity of storage allocated for a host. For thin LUNs in All-Flash pools, data reduction is allowed to save space. You can allocate a LUN to more than one host, if you coordinate the access by using a set of clustered hosts. After a LUN is created individually or as part of a consistency group, individual hosts can map to the LUN based on the settings and permissions configured through Unisphere.
    Consistency group
    An addressable instance of LUN storage that can contain one or more LUNs (up to 50) and is associated with one or more attached hosts. Consistency groups help organize the storage allocated for a particular host or hosts. Snapshots taken of a consistency group apply to all LUNs associated with the group.
    Storage hosts (Initiators)

    Storage hosts are systems that use storage system LUN resources. Before a host can access storage resources, you must define a configuration for it through Unisphere with the Host wizard. A host configuration specifies the host name and one or more initiators (FC WWN or iSCSI IQN). After defining the host configuration, you can also specify the type of access that the host has to the LUN or consistency group. The host can then map from the host-side to any LUNs associated with a consistency group. Refer to the host documentation for more information.

    Create a LUN

    Before you begin

    Before you create a LUN, at least one pool must exist on the storage system. Obtain the following information:

    • Storage size you want to allocate for the LUN.
    • Information about the host that will use the LUN (if a host configuration does not exist), including the host's iSCSI address or WWN, CHAP secret (if applicable), and type of access (storage, snapshot, or both) to allow.
    • Protection schedule including the frequency with which to perform automatic snapshots and the length of time to retain individual snapshots.
    Procedure
    1. Under Storage, select Block > LUNs.
    2. Select the Add icon.
      Note:  You can also create LUNs when you create a new consistency group.
    3. Specify the relevant information, while noting the following:
      • You can specify a Host LUN ID of your choosing. If one is not specified, the system will assign one by default.
      • If you are adding LUNs from the Host Properties window, you can specify Host LUN IDs when creating new LUNs by using the Assign Host LUN IDs button. You cannot specify Host LUN IDs when adding existing or multiple LUNs to the host, but you can modify them after they are added to the host.
      • After you create the LUN, you can increase its size but not decrease it.
      • You can create multiple LUNs at once with a maximum limit of 100 LUNs. The system appends the LUN name with a number when creating multiple LUNs.
      • The Size value displays the quantity of storage subscribed for the LUN.
      • If you want to limit I/O throughput and bandwidth to provide more predictable performance, select an existing host I/O limit policy to enforce on this LUN or create a new policy.
      • The Thin checkbox is selected by default. If you do not want to create a thin LUN, remove the checkmark from the Thin checkbox. Removing the checkmark also disables the Data Reduction option.
      • The Data Reduction checkbox is available for thin LUNs in All-Flash pools only. It allows a thin LUN to have data reduction applied to save space.
      • The Advanced Deduplication checkbox becomes available only when the Data Reduction checkbox is enabled. It provides the ability to reduce the amount of data storage needed by eliminating redundant data from the system. Once enabled, all incoming writes to the system will have advanced deduplication applied.

        Advanced Deduplication is available on:

        • Dynamic or Traditional pools in Unity 380F, 480F, 680F, and 880F systems
        • Dynamic pools in Unity All-Flash 450F, 550F, and 650F systems
        • All-Flash pools in Unity Hybrid 380, 480, 680, and 880 systems
      • If a resource contains snapshots or thin clones, either data reduction or both data reduction and advanced deduplication might be enabled on the snapshots or thin clones, depending on the source's settings.

    Change LUN or LUN thin clone properties

    Procedure
    1. Under Storage, select Block > LUNs.
    2. Select the relevant LUN or thin clone, and then select the Edit icon.
    3. On the General tab:
      • Change the LUN or thin clone name, description, and size, and view space usage and capacity information.
      • You can change the default SP owner for a LUN, but not for a thin clone.
      • If you change the default SP owner for a base LUN, the default SP changes automatically for its derivative thin clones.
      • If this is a thin LUN or a file system in an All-Flash pool, you can choose to apply data reduction to all incoming writes by selecting the Data Reduction checkbox.
        Note:  To apply data reduction to both incoming LUN writes and existing LUN data, you must use the LUN Move session feature to move the LUN's data to a destination LUN that has data reduction enabled. It is recommended that you perform a LUN Move operation only on a single LUN for an SP at a time, and not perform multiple move operations on an SP simultaneously. Refer to About LUN Move sessions for additional LUN Move information.
      • You can also enable Advanced Deduplication if the Data Reduction checkbox is enabled. Advanced deduplication is available on Unity All-Flash 450F, 550F, and 650F systems only. It provides the ability to reduce the amount of data storage needed by eliminating redundant data from the system. Once enabled, all incoming writes to the system will have advanced deduplication applied.
      • If the LUN already has data reduction applied, you can view the capacity: how much space is allocated after data reduction was applied, and the space saved due to applying data reduction to this LUN, including its snapshots and thin clones. Data reduction savings are shown in multiple formats, including actual space saved (GB/TB), ratio, and percentage.
      • You can also choose to disable data reduction by removing the checkmark from the Data Reduction checkbox and clicking the Apply button. Existing data remains as is until overwritten. Any newly-written data does not have data reduction applied.
      • You can also choose to disable advanced deduplication by removing the checkmark from the Advanced Deduplication checkbox and clicking the Apply button. Existing data remains as is until overwritten. Any newly-written data does not have advanced deduplication applied.
      • A thin clone cannot have data reduction applied independently of its base LUN. However, if you apply data reduction to the base LUN, the thin clone also has data reduction applied.
      • If a LUN is in the process of being moved, you can view the status and change the move session's priority setting. If the move is completed, you can view the move status for up to three days after the operation completed.
        Note:  A thin clone or a LUN that has a thin clone cannot be moved.
    4. On the Host Access tab, modify the list of hosts that have access to the LUN or thin clone, modify the Host LUN ID for a specific host, or change the type of access.
    5. On the FAST VP tab, change the tiering policy and view the data distribution per tier.
      Note:  You cannot change the tiering policy for a thin clone independently of its base LUN. However, if you change the tiering policy of the base LUN, the thin clone inherits the changed tiering policy.
    6. On the Snapshots tab, manage the LUN or thin clone's snapshots or configure a snapshot schedule for the LUN.
    7. On the Replication tab, configure replication settings. Select Configure Replication to get started.
      Note:  When you replicate a thin clone, it becomes a standard LUN on the destination storage system, with no ties to the original base LUN.
    8. On the Host I/O Limit tab, view the bandwidth and throughput performance of the LUN or thin clone with the current policy, select a different policy and preview the performance impact of that policy, or apply a new policy.

    Delete a LUN

    Before you begin

    You should delete a LUN only if:

    • The LUN was used for testing purposes and the tests have completed.
    • The LUN has been replicated to a different destination and the source LUN is no longer needed.
    • You are trying to save space by deleting the LUN and the data on that LUN is no longer needed.
    Note:  LUN deletion is an irreversible operation.
    Ensure the following conditions are met before attempting to delete a LUN:
    • The LUN does not have any attached snapshots.
    • The LUN does not have any active replication sessions.
    • The LUN is not currently attached to hosts.
      Note:  LUNs cannot be deleted if hosts are currently attached. Remove host access before deleting any LUNs. Plan host downtime where needed, or ensure the hosts no longer need the LUN before removing access. If you are migrating hosts from one LUN to another, ensure the hosts have access to the new LUN before removing them from the LUN that will be deleted.
    Procedure
    1. Under Storage, select Block > LUNs.
    2. Select the relevant LUN, and click the Delete icon.
      If the Delete icon is not available, the LUN currently has hosts attached. Use the following steps to remove access from the LUNs and retry the deletion:
      1. Make sure the LUN you want to delete is selected.
      2. Ensure any currently attached hosts no longer need the LUN. Under More Actions, click Modify Host Access.
      3. Review the list of attached hosts. Select all the hosts, click the Delete icon, and then click Delete to confirm.
        When the job completes, the Delete icon will become available for the selected LUN.
    Results
    If the job fails, check the job details on the Jobs page for more information. The LUN deletion may be prevented due to one of the scenarios listed above.

    About iSCSI interfaces

    iSCSI interfaces enable hosts using the iSCSI protocol to access block storage (LUNs, consistency groups, and VMware VMFS datastores) on the storage system. The iSCSI interfaces provide continuous access to data when a Storage Processor (SP) becomes unavailable because of a system software upgrade or component failure. When you add an iSCSI interface on the storage system, you associate it with one or both Storage Processors (SPs). So, at a given point, there will be multiple iSCSI interfaces on each SP. These become the available paths hosts, with relevant access privileges, can use to access the relevant storage resources.

    Note:  Fibre Channel interfaces are created automatically on the storage system.

    To ensure continuous access to the storage in an event of a failover, set up iSCSI interfaces on the same port of each SP, and then leverage host-based multipathing software to manage multiple connections to the storage system.

    Add or edit iSCSI interfaces

    When you log on to Unisphere for the first time, the Initial Configuration Wizard includes a step that enables you to add iSCSI interfaces. To add or manage iSCSI interfaces at a later time, under Storage, select Block > iSCSI Interfaces.

    Note:  iSCSI interfaces can only be created on an Ethernet port that is not participating in a link aggregation.

    Before you begin creating or updating an iSCSI interface, ensure that you have the following information:

    • The Ethernet port you will use for the iSCSI interface.
    • For each Storage Processor (SP), the following address information:
      • IP address associated with the iSCSI interface. Although you can specify an IPv4 or IPv6-based address, ensure that you specify the same type of address for both SPs.
      • IP address mask or prefix length that identifies the subnet where the iSCSI interface resides.
      • Gateway IP address associated with the iSCSI interface.
      • Alias name associated with the IQN. The IQN and the IQN alias are associated with the port, and not the iSCSI interface. When you change the IQN alias for an iSCSI interface, the alias changes for all interfaces on that port.
    • If applicable, the VLAN ID (between 1 and 4904) you want to associate the iSCSI interface with.
      Note:  For the network to continue functioning properly, ensure that you set the VLAN ID only when you have configured the network switch port to support VLAN tagging of multiple VLAN IDs.

    Create a consistency group

    Procedure
    1. Under Storage, select Block > Consistency Groups.
    2. Select the Add icon.
    3. Specify the relevant information.

    Add a LUN to a consistency group

    Procedure
    1. Under Storage, select Block > Consistency Groups.
    2. Select a consistency group from the list.
    3. Select Add LUNs.
    4. Specify the relevant information, while noting the following:
      • You can create one or more new LUNs and add them to the consistency group.
      • Or you can move existing LUNs that are not already assigned to a consistency group to a consistency group.

    Change consistency group or consistency group thin clone properties

    Procedure
    1. Under Storage, select Block > Consistency Groups.
    2. Select the relevant consistency group or thin clone, and then select the Edit icon.
    3. On the General tab, change a consistency group or thin clone name and description. and view space usage and capacity information.
    4. On the LUNs tab, add or remove LUNs from the consistency group or thin clone. You can change the default SP owner for a LUN, but not a thin clone. If you change the default SP owner for a base LUN, the default SP changes automatically for its derivative thin clones.

      If this is a thin LUN in an All-Flash pool, you can choose to apply data reduction to all incoming writes by selecting the Data Reduction checkbox.

      Note:  To apply data reduction to both incoming LUN writes and existing LUN data, you must use the LUN Move session feature to move the LUN's data to a destination LUN that has data reduction enabled. It is recommended that you perform a LUN Move operation only on a single LUN for an SP at a time, and not perform multiple move operations on an SP simultaneously. Refer to About LUN Move sessions for additional LUN Move information.
      • If the LUN already has data reduction applied, you can view the capacity: how much space is allocated after data reduction was applied, how much space is not allocated, and the space saved for the entire system after data reduction.
      • You can also choose to disable data reduction by removing the checkmark from the Data Reduction checkbox and clicking the Apply button. Existing data remains as is. Any newly-written data does not have data reduction applied.
      • If a LUN is in the process of being moved, you can view the status and change the move session's priority setting. If the move is completed, you can view the move status for up to three days after the operation completed.
      • A thin clone cannot have data reduction applied independently of its base LUN. However, if you apply data reduction to the base LUN, the thin clone also has data reduction applied.
    5. On the Access tab, modify the list of hosts that have access to the LUNs in the consistency group or thin clone, or change the type of access.
    6. On the FAST VP tab, change the tiering policy and view the data distribution per tier.
      Note:  You cannot change the tiering policy for a thin clone independently of its base LUN in the consistency group. However, if you change the tiering policy of the base LUN, the thin clone inherits the changed tiering policy.
    7. On the Snapshots tab, manage the consistency group's or thin clone's snapshots or configure a snapshot schedule for the LUN or thin clone.
    8. On the Replication tab, configure replication settings. Select Configure Replication to get started.
      Note:  When you replicate a thin clone, it becomes a standard LUN on the destination storage system, with no ties to the original base LUN.

    Delete a consistency group

    Before you begin
    Note:  Deleting a consistency group will also delete any of its snapshots, as well as all of the LUNs in that group. If the consistency group contains LUNs with attached hosts, you cannot delete the consistency group.
    Procedure
    1. Under Storage, select Block > Consistency Groups.
    2. Select the relevant consistency group, and then select the Delete icon.
      If the Delete icon is not available, one or more of the LUNs in the consistency group currently has hosts attached. Remove access from the group LUNs and retry the deletion.
      1. Select the consistency group you want to delete.
      2. Ensure any currently attached hosts no longer need the LUNs in the consistency group. Under More Actions, click Remove Host Access.
      3. Review the list of attached hosts for each LUN in the consistency group. Click Remove Host Access to confirm.
        When the job completes, the Delete icon will become available for the selected consistency group.
    Results
    If the job fails, check the job details on the Jobs page for more information. The consistency group deletion may have been prevented if any LUNs within it have attached hosts.