## N_Port ID Virtualization (NPIV) mode 

In this mode, the cache device is available as a virtual Fibre Channel (FC) device on the AIX LPAR. A cache pool can be created on the AIX LPAR on which only one cache partition may be created. The cache partition can be used to cache any number of target devices on this LPAR. Because the cache device is available from the SAN, the LPAR can be migrated to another server. The cache device must be made visible on the target system. Caching can continue to occur throughout the migration process, and the cache continues to stay populated after the migration completes. 

In the following scenario, we have hdisk1 as a cache version, and hdisk2 as a target device. 

Complete the following steps: 

1. Create a cache pool and a cache partition, as shown in Example 1-15. 

# cache_mgt pool create -d hdisk1 -p pool1 # cache_mgt partition create -p pool1 -s 1000M -P part1 

2. Assign the cache partition to target device hdisk2 in which we want to cache, as described in Example 1-16. 

# cache_mgt partition assign -t hdisk2 -P part1 

3. Start caching on the target device and monitor the status, as shown in Example 1-17. 

## 1.3 Multipath I/O 

# cache_mgt cache start -t hdisk2 # cache_mgt monitor get –h -s 

Multipath I/O (MPIO) provides the ability for a device to be accessed through one or more storage paths. To use MPIO, you need two main components: 

GLYPH<SM590000> An MPIO-capable device driver that controls the target device. 

GLYPH<SM590000> A path control module (PCM) that provides path management functions. 

As of AIX 7.2 TL 3, the parallel SCSI, iSCSI, and FC disk device drivers and their device methods support MPIO disk devices. In this section, we describe the AIX Path Control Module (AIXPCM). 

## 1.3.1 AIX Path Control Module 

The native AIXPCM performs path management functions and health checks. The health check capabilities of AIXPCM allow it to: 

GLYPH<SM590000> Check the paths and determine which paths are usable for sending I/O. 

GLYPH<SM590000> Enable a path that was previously marked failed because of a temporary path fault. 

GLYPH<SM590000> Check unused paths that would be used if a failover occurred. 

