vSphere Storage - ESXi 5.1 - Documentation - VMware
vSphere Storage - ESXi 5.1 - Documentation - VMware
vSphere Storage - ESXi 5.1 - Documentation - VMware
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6 The SATP interprets the I/O command errors and, when appropriate, activates the inactive paths.<br />
7 The PSP is called to select a new path on which to issue the I/O.<br />
Path Scanning and Claiming<br />
When you start your <strong>ESXi</strong> host or rescan your storage adapter, the host discovers all physical paths to storage<br />
devices available to the host. Based on a set of claim rules, the host determines which multipathing plug-in<br />
(MPP) should claim the paths to a particular device and become responsible for managing the multipathing<br />
support for the device.<br />
By default, the host performs a periodic path evaluation every 5 minutes causing any unclaimed paths to be<br />
claimed by the appropriate MPP.<br />
The claim rules are numbered. For each physical path, the host runs through the claim rules starting with the<br />
lowest number first. The attributes of the physical path are compared to the path specification in the claim rule.<br />
If there is a match, the host assigns the MPP specified in the claim rule to manage the physical path. This<br />
continues until all physical paths are claimed by corresponding MPPs, either third-party multipathing plugins<br />
or the native multipathing plug-in (NMP).<br />
For the paths managed by the NMP module, a second set of claim rules is applied. These rules determine which<br />
<strong>Storage</strong> Array Type Plug-In (SATP) should be used to manage the paths for a specific array type, and which<br />
Path Selection Plug-In (PSP) is to be used for each storage device.<br />
Use the <strong>vSphere</strong> Client or the <strong>vSphere</strong> Web Client to view which SATP and PSP the host is using for a specific<br />
storage device and the status of all available paths for this storage device. If needed, you can change the default<br />
<strong>VMware</strong> PSP using the client. To change the default SATP, you need to modify claim rules using the <strong>vSphere</strong><br />
CLI.<br />
You can find some information about modifying claim rules in “Managing <strong>Storage</strong> Paths and Multipathing<br />
Plug-Ins,” on page 205.<br />
For more information about the commands available to manage PSA, see Getting Started with <strong>vSphere</strong> Command-<br />
Line Interfaces.<br />
For a complete list of storage arrays and corresponding SATPs and PSPs, see the SAN Array Model Reference<br />
section of the <strong>vSphere</strong> Compatibility Guide.<br />
Viewing the Paths Information<br />
You can review the storage array type policy (SATP) and path selection policy (PSP) that the <strong>ESXi</strong> host uses<br />
for a specific storage device and the status of all available paths for this storage device. You can access the path<br />
information from both the Datastores and Devices views. For datastores, you review the paths that connect to<br />
the device the datastore is deployed on.<br />
The path information includes the SATP assigned to manage the device, the PSP, a list of paths, and the status<br />
of each path. The following path status information can appear:<br />
Active Paths available for issuing I/O to a LUN. A single or multiple working paths<br />
currently used for transferring data are marked as Active (I/O).<br />
Standby If active paths fail, the path can quickly become operational and can be used<br />
for I/O.<br />
Disabled The path is disabled and no data can be transferred.<br />
Chapter 20 Understanding Multipathing and Failover<br />
Dead The software cannot connect to the disk through this path.<br />
If you are using the Fixed path policy, you can see which path is the preferred path. The preferred path is<br />
marked with an asterisk (*) in the Preferred column.<br />
<strong>VMware</strong>, Inc. 201