Using Persistent Reservations

The option enables you to view and clear and associated . Persistent reservations, which are configured and managed through the cluster server software, preserve virtual disk reservations and registrations and prevent other from accessing the .

Caution: Risk of application errors -- Persistent reservations are allowed on a in a but are not allowed on a . If a virtual disk has any type of reservation when designated as a secondary virtual disk, the primary virtual disk detects a reservation conflict at its first write request to the secondary virtual disk and clears the reservation automatically. Subsequent requests to place a reservation on the secondary virtual disk are rejected.

Important:

This option should be used only under the guidance of a Customer and Technical Support representative.
A virtual disk with a different type of reservation (for example, SCSI-2 reservations) cannot also have persistent reservations. However, different virtual disks can have different types of reservations.
A virtual disk with persistent reservations or registrations rejects all other types of reservation commands with a Reservation Conflict status. Likewise, a virtual disk with other types of reservations rejects all persistent reservation commands with a Reservation Conflict status.
Virtual Disks holding a persistent reservation cannot be used as or candidates for virtual disk copy operations.
You must clear persistent reservations before you can change a LUN mapping or delete a LUN mapping on a virtual disk holding a reservation.
Deletion of virtual disks or deletion of disk groups with any type of persistent reservation is not allowed and returns an error status. However, you can delete virtual disks and disk groups containing only registrations.
Deletion of missing virtual disks containing registrations or reservations is allowed.

For quick access to information about a particular procedure, click one of the following links:

How to Interpret Persistent Reservation Data
How to Save Reservation/Registration Details
How to Clear Virtual Disk Reservations

Viewing Virtual Disk Reservations and Registrations

Select any desired node in the , and then select Advanced >> Maintenance >> Persistent Reservations in the Logical View.

The dialog displays any virtual disks in the that have registrations, with the first virtual disk in the list highlighted by default.

Interpreting Persistent Reservation Data

The dialog displays any virtual disks in the storage array that have registrations, with the first virtual disk in the list highlighted by default. If there are no virtual disks with registrants, the dialog shows no data. The following table describes the information and buttons displayed in the Persistent Reservation dialog.

Virtual Disk Name

Displays the user label of the virtual disk with persistent reservations. Virtual Disks are listed in alphabetical order. If a virtual disk user label is not available, then its virtual disk identifier (WWN) is shown.

LUN

Displays the assigned number for the particular virtual disk.

Registrations

Displays the number of registrations for the particular virtual disk.

Reservation Type

Displays an abbreviated form of the associated Reservation Type for the particular virtual disk.

Each addressable virtual disk can have one reservation, and each reservation can grant access rights to one or more registrants, depending on the reservation type. A virtual disk can be reserved for a specific access level by a group of registrants. All registrants within a group are restricted to the access level defined by the reservation type. Reservation types are shown in the following table:

None	The virtual disk has registrants, but currently has no reservation.
WE = Write Exclusive	Writes exclusive: Only the that reserved the virtual disk might write to the virtual disk. Reads shared: Any HBA host port might read from the virtual disk.
EA = Exclusive Access	Only the HBA host port that reserved the virtual disk might read or write to the virtual disk.
WE-RO = Write Exclusive - Registrants Only	Writes exclusive: All registered HBA host ports might write to the virtual disk. Reads shared: Any HBA host port might read from the virtual disk.
EA-RO = Exclusive Access - Registrants Only	Only registered HBA host ports might read or write to the virtual disk.
WE-AR = Write Exclusive - All Registrants	Writes exclusive: All registered HBA host ports might write to the virtual disk. Reads shared: Any HBA host port might read from the virtual disk.
EA-AR = Exclusive Access - All Registrants	Only an HBA host port might read or write to the virtual disk.

PTPL?

Displays Yes if the registrations are set to persist through a power loss.

To view the registrations associated with the virtual disk reservation, double-click the desired virtual disk or highlight the virtual disk and select the View Associated Registrations check box in the upper-left of the dialog.

Important: You can view only one virtual disk's registration at a time.

The following table describes the information displayed in the Persistent Reservation dialog showing virtual disk registrations.

Interface Type	Displays the type of interface: SATA, PATA, or Fibre.
Host (Initiator) Port	Displays the associated user label for the particular host port. If the host port alias has not been provided, then "Not Available" is displayed.
Associated Host	Displays the host associated with the particular virtual disk.
RAID Controller Module (Target) Ports	Displays the port name of the target port.
Holds Reservation?	Displays either Yes or No, depending on whether the particular HBA host port is the reservation holder. If the registrant holds the reservation, the RAID controller module port that holds the reservation is indicated. For example, Yes (A1), Yes (B2). If the reservation type is such that all ports hold the reservation, then the designation is Yes (list of applicable RAID controller module ports). For example, Yes (A1, A2, B1). For certain reservation types, all registrants for the specific virtual disk are considered reservation holders, and each registrant has "Yes" under this column. In most cases, only one registrant holds the reservation.

Use the Refresh option to update the reservation and registration view. An hourglass is displayed while the reservation and registration information is updated. The first virtual disk in the list should be highlighted. If the check box was selected before the Refresh button was selected, it remains checked, and the reservation information shown in the bottom pane for the virtual disk is highlighted.

Saving Reservation and Registration Details

Use the Save As option to save all reservation and registration information. All reservation and registration information for each virtual disk is saved, no matter how many virtual disks you have highlighted in the upper pane. Perform the following steps:

1	Click Save As.
2	Navigate to the directory in which you will save the file.
3	Enter the name of the file in the field.
4	Click Save. The Files of Type field will list All Files (.) and Reservation data (.txt). The Reservation data (.txt) should be the default file shown. The file will be saved as a `.txt` file which will be an ASCII-representation of the registration/reservation information.

Clearing Virtual Disk Reservations

Virtual Disk reservation and registration data for HBA host ports no longer part of the configuration might be retained along with current registration and reservation data. Accumulation of the old data eventually can cause the to reach the upper boundary of allowed HBA host ports and to issue an Insufficient Registrations Resources error if another HBA host port attempts to register. The maximum number of registrants per virtual disk is 512; the maximum number of registrants per storage array of total registrations is 100,000.

Important:

To prevent an Insufficient Registration Resources error, clear old data associated with a virtual disk when it no longer has a reservation. Clear old data during scheduled downtime maintenance to prevent interference with cluster server operations.
This option clears the reservation and all associated registrations for the virtual disks you have selected. This option does not let you clear a particular reservation or registration for a selected virtual disk.

Use the Clear option to:

Release virtual disk reservations and remove associated registrations when the HBA host port is no longer part of the configuration.
Clear old data associated with a virtual disk that no longer has a reservation.

1	Ensure that the View Associated Registrations check box is deselected.
2	Click one or more desired virtual disks. To select all virtual disks, click Select All.
3	Click Clear.
4	Type `yes` in the confirmation field, and click OK.
5	Click Cancel to return to the main Persistent Reservations dialog without clearing any reservations.