HP StorageWorks 2000 Modular Smart Array Reference Guide (481599-003, August 2008)

186 HP StorageWorks 2000 Family Modular Smart Array reference guide • August 2008
Clearing Unwritable Cache Data
The controller cache contains data that cannot be written out to a virtual disk
because that virtual disk is no longer accessible. The virtual disk might be offline or
missing. Unwritable cache data can exist if I/O to the virtual disk does not complete
because drives or enclosures fail or are removed before the data can be written.
Recovery is possible if the missing devices can be restored so that the cached data
can be written to the virtual disk. Unwritable cache data might affect performance
because it ties up the cache space and prevents that space from being used by other
virtual disks performing I/O.
Using SMU, you can view the percentage of storage system cache capacity that is
occupied by unwritable data and delete that data.
The unwritable data may represent data for one or more volumes.
Caution – Before clearing unwritable data, make sure it is no longer needed. The
data cannot be recovered after being cleared.
To clear unwritable cache data:
1. Select Manage > Utilities > Recovery Utilities > Cache Data Status.
If there is no unwritable cache data, a message says so. If there is unwritable cache
data, the page shows the percentage of storage system cache capacity that the data
occupies, and the serial number of the related volume.
Note – Related event log messages show the percentage of capacity for the owning
controller only. For example, if unwritable data occupies 4% of the owning
controller's cache, and this is a dual-controller system, the event log shows 4%
while the Cache Data Status page shows 2%.
2. Click Clear Unwritable Cache Data.
The unwritable data is cleared for the specified volume. The page displays the serial
number of the next volume having unwritable data, if any.
Repeat as necessary to clear all unwritable data.