Storage System Shutdown And Startup; Shutting Down The Storage System From Hp Command View Eva - HP StorageWorks 4400 User Manual

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 Command View EVA 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 drive enclosures
5. Disconnects the system from HP Command View EVA
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.

Shutting down the storage system from HP Command View EVA

1.
Start HP Command View EVA.
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.
40 EVA4400 operation