Administrator Guide

3 Right-click the volume and select Map Volume to Server.
4 In the Map Volume to Server window, select the server.
5 Click Next.
6 Select Enable Fluid Cache.
7 From the Host Cache Policy drop-down menu, select a cache mode:
• Write-back (default): In addition to caching reads, write-back mode allows the caching of written
data without waiting for the Compellent Array to acknowledge the write operation. Write-back
caching requires a cache device on two or more servers in the cluster.
• Write-through: Write-through mode forces writes to both the cache and the Compellent Array
simultaneously. Warm reads and read-after writes are accelerated but write operations are not.
Write-through caching requires only one cache device on one server in the cluster.
NOTE: The cache mode selected for a volume mapping cannot be changed. To select a different
cache mode, you must remove the mapping and create a new mapping. When you create the new
mapping, you can then select a different cache mode.
8 (Optional) Select the Keep cached data on the node that accessed the data option. Selecting this
option gives the best performance for warm reads from the cache for datasets that fit on the local
node’s cache devices, because all data is local to the client. If this option is not selected, cached data is
evenly distributed among all cache devices.
9 Click Finish.
At this stage, there is a delay while the system makes a number of configuration changes.
Mapping Volumes to a Subcluster
Before mapping volumes to a subcluster, create a Fluid Cache cluster (see Creating a Fluid Cache Cluster) and
a server cluster (“subcluster”) within it.
To map a volume to a subcluster, follow the procedure for mapping a volume to a server (see previous
section), but instead of selecting a server in the Map Volume to Server window (step 4), select a subcluster
within a Fluid Cache cluster.
Although not specific to Fluid Cache, be aware of these aspects of volume mappings created at the
subcluster level in Enterprise Manager:
• When servers are added to or removed from the subcluster, they automatically inherit or disinherit the
subcluster’s volume mappings.
• You can promote a volume mapping from a server to the subcluster, and demote it from the cluster to
the subcluster.
• If a server has existing mappings, the server keeps those mappings when it becomes part of a subcluster.
Removing Volume Mappings
To see a list of Fluid Cache mappings, select the appropriate Storage Center in the Storage view, and in the in
the Storage tab, select the Fluid Cache cluster. The Fluid Cache mappings for the cluster are listed in the
Volumes area at the bottom of the page.
Fluid Cache for SAN Cluster Creation and Management Operations 26