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purehost-connect

Name

purehost-connect, purehost-disconnect, purevol-connect, purevol-disconnect — manage private connections between hosts and volumes

Synopsis

purehost connect --vol VOL [--lun LUN] HOST...

purehost disconnect --vol VOL HOST...

purevol connect { --host HOST | --hgroup HGROUP } [--lun LUN] VOL...

purevol disconnect { --host HOST | --hgroup HGROUP } VOL...

Arguments

HOST

Name of a host to be connected to or disconnected from a volume.

VOL

Name of a volume to be connected to or disconnected from a host.

Options

-h | --help

Can be used with any command or subcommand to display a brief syntax description.

--hgroup

Host group with which shared connections to the specified volumes are to be made or broken by purevol connect and purevol disconnect commands. Exactly one host group must be specified by this option. The option is mutually exclusive with the --host option.

--host

Host with which private connections to the specified volumes are to be made or broken by purevol connect and purevol disconnect commands. Exactly one host must be specified by this option. The option is mutually exclusive with the --hgroup option.

--lun

Logical unit number (LUN) by which specified hosts are to address specified volume. If not specified, Purity automatically assigns a LUN to the connection. To automatically assign a LUN to a private connection, Purity starts at LUN 1 and counts up to the maximum LUN 4095, assigning the first available LUN to the connection.

--vol

Volume with which private connections to the specified hosts are to be made or broken by purehost connect and purehost disconnect commands. Exactly one volume must be specified by this option.

Description

Makes and breaks private connections between hosts and volumes and shared connections between hosts associated with host groups and volumes.

For private connections:

  • The purehost connect and purehost disconnect commands are used to manage private connections between a single volume and one or more hosts.

  • The purevol connect and purevol disconnect commands are used with the --host option to manage private connections between a single host and one or more volumes.

For shared connections:

  • The purevol connect and purevol disconnect commands are used with the --hgroup option to manage shared connections between a single host group and one or more volumes. See purehgroup-connect(1) for additional commands used to manage shared connections.

Private vs. Shared Host-Volume Connections

Purity supports two types of host-volume connections:

Private

Connects one volume to one host. Private connections are independent of one another. For example, the sequence:

  purevol connect --host HOST1 VOL1 VOL2
  purehost disconnect --vol VOL1 HOST1
              

connects HOST1 to VOL1 and HOST1 to VOL2, and then disconnects HOST1 and VOL1, leaving HOST1 connected to VOL2.

Private connections are typically used for boot volumes and for stand-alone (non-clustered) host applications.

To establish a private connection, run the purevol connect --host or purehost connect --vol command. Both commands are functionally identical.

To break a private connection that is no longer required, run the purevol disconnect --host or purehost disconnect --vol command. Both commands are functionally identical. When a connection has been broken, its LUN is available for reuse.

Shared

Connects a designated set of hosts (via a host group) to a designated set of volumes, providing the hosts with a consistent "view" of the volumes. All associated hosts use the same LUN to address a given associated volume. All hosts and volumes associated with a host group are automatically connected to each other by virtue of their associations with the group.

To establish a shared connection (assuming the host belongs to a host group), run the purevol connect --hgroup or purehgroup connect --vol command. Both commands are functionally identical. For example, the command:

purevol connect --hgroup HGROUP1 VOL1 VOL2
              

is equivalent to the sequence:

purehgroup connect --vol VOL1 HGROUP1
purehgroup connect --vol VOL2 HGROUP1
              

Both commands establish shared connections between the hosts associated with HGROUP1 and VOL1 and VOL2.

Shared connections are useful for cluster applications in which several related hosts require consistent (same LUN) connectivity to a set of storage volumes.

To break a shared connection that is no longer required, run the purevol disconnect --hgroup or purehgroup disconnect --vol command. Both commands are functionally identical. When a connection has been broken, its LUN is available for reuse.

For more information about shared connections and the purehgroup connect command, refer to purehgroup-connect(1).

A host can have only one connection to a given volume at any given time. If you attempt to make a second connection between a host and a volume, private or shared, the attempt will fail.

App Hosts

The Apps platform extends array functionality by integrating add-on, VM-based services into the Purity operating system. Each app within the platform provides one or more services.

Each app has a dedicated host, known as an app host. The app host is used to connect FlashArray volumes to the app.

Run the purehost connect --vol or purevol connect --host command to connect FlashArray volumes to an app host, and thereby its associated app. Likewise, run the purehost disconnect --vol or purevol disconnect --host command to break the connection between the FlashArray volumes and the app.

For more information about Pure Apps and the pureapp command, refer to pureapp(1).

LUN Management

When a volume is connected to a host, it is assigned a logical unit number (LUN) ID, which the host uses to communicate with the volume. A volume can be connected to individual hosts as well as to multiple host groups simultaneously. Include the --lun option with the purehost connect or purevol connect --host command to manually assign a LUN ID anywhere in the [1...4095] range.

If you do not manually specify a LUN, Purity automatically assigns a LUN to the private connection. To do this, Purity starts at LUN 1 and counts up to the maximum LUN 4095, assigning the first available LUN to the connection.

If multiple hosts are specified in a single purehost connect command, there is no guarantee that the same LUN will be associated with each connection established. When --lun and --host are both specified in a purehost connect or purevol connect command, exactly one host and one volume must be specified.

To change the LUN associated with a private connection, the connection must first be broken and then recreated by purehost connect or purevol connect.

Exceptions

Purity will not establish a (private) connection between a volume and a host if:

  • An unavailable LUN was specified.

  • The volume is already connected to the host, either through a private or shared connection.

Examples

Example 1

purevol connect --host HOST1 VOL1 VOL2
      

Establishes private connections between HOST1 and VOL1 and between HOST1 and VOL2.

Purity assigns a LUN to each connection. If HOST1 is associated with a host group, Purity assigns a LUN according to the LUN assignment guidelines for shared connections. If HOST1 is not associated with a host group, Purity assigns a LUN according to the LUN assignment guidelines for private connections.

Example 2

purehost connect --vol VOL3 --lun 4 HOST2
purevol connect --host HOST2 --lun 5 VOL4
      

Establishes private connections between HOST2 and VOL3 and between HOST2 and VOL4. If LUN 4 or LUN 5 is already in use by another connection to HOST2, the corresponding connection fails.

Example 3

purevol connect --host @linux app__vol001
      

Connects FlashArray volume app_vol001 to the linux app via app host @linux.

Example 4

purehost disconnect --vol app_vol002 @linux
      

Breaks the connection between FlashArray volume app_vol002 and the linux app.

Author

Pure Storage Inc.