User's Manual

Implicit LUN transition
Implicit LUN transition automatically transfers management of a virtual disk to the array controller
that receives the most read requests for that virtual disk. This improves performance by reducing
the overhead incurred when servicing read I/Os on the non-managing controller. Implicit LUN
transition is enabled in XCS.
When creating a virtual disk, one controller is selected to manage the virtual disk. Only this
managing controller can issue I/Os to a virtual disk in response to a host read or write request. If
a read I/O request arrives on the non-managing controller, the read request must be transferred
to the managing controller for servicing. The managing controller issues the I/O request, caches
the read data, and mirrors that data to the cache on the non-managing controller, which then
transfers the read data to the host. Because this type of transaction, called a proxy read, requires
additional overhead, it provides less than optimal performance. (There is little impact on a write
request because all writes are mirrored in both controllers’ caches for fault protection.)
With implicit LUN transition, when the array detects that a majority of read requests for a virtual
disk are proxy reads, the array transitions management of the virtual disk to the non-managing
controller. This improves performance because the controller receiving most of the read requests
becomes the managing controller, reducing proxy read overhead for subsequent I/Os.
Implicit LUN transition is disabled for all members of an HP Continuous Access EVA DR group.
Because HP Continuous Access EVA requires that all members of a DR group be managed by the
same controller, it would be necessary to move all members of the DR group if excessive proxy
reads were detected on any virtual disk in the group. This would impact performance and create
a proxy read situation for the other virtual disks in the DR group. Not implementing implicit LUN
transition on a DR group may cause a virtual disk in the DR group to have excessive proxy reads.
Storage system shutdown and startup
You can shut down the array from HP P6000 Command View or from the array controller.
The shutdown process performs the following functions in the indicated order:
1. Flushes cache
2. Removes power from the controllers
3. Disables cache battery power
4. Removes power from the disk enclosures
5. Disconnects the system from HP P6000 Command View
NOTE: The storage system may take several minutes (up to 15) to complete the necessary cache
flush during controller shutdown when snapshots are being used. The delay may be particularly
long if multiple child snapshots are used, or if there has been a large amount of write activity to
the snapshot source virtual disk.
Individual EVA storage array components should not be powered off during normal operation.
Before powering off any storage system component, contact your HP-authorized service
representative for assistance.
Shutting down the storage system from HP P6000 Command View
1. Start HP P6000 Command View.
2. Select the appropriate storage system in the Navigation pane.
The Initialized Storage System Properties window for the selected storage system opens.
3. Click Shut down.
The Shutdown Options window opens.
32 EVA4400 operation