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Because the optimal number of volume paths is four, you must create two or more hosts on FlashSystem 9100. During volume assignment, alternate which volume is assigned to each of the “pseudo-hosts,” in a round-robin fashion. 

Note:  Pseudo-hosts is not a defined function or feature of SAN Volume Controller/ Storwize. To create a pseudo-host, you simply need to add another host ID to the SAN Volume Controller and Storwize host configuration. Instead of creating one host ID with four WWPNs, you define two hosts with two WWPNs, therefore you need to pay extra attention to the scsi ids assigned to each of the pseudo-hosts to avoid having 2 different volumes from the same storage subsystem with the same scsi id. 

## ESX Cluster zoning 

For ESX Clusters, you must create separate zones for each host node in the ESX Cluster as shown in Figure 2-16. 

<img src='content_image/971194.jpg'>

Ensure that you apply the following preferred practices to your ESX VMware clustered hosts configuration: 

GLYPH<SM590000> Zone a single ESX cluster in a manner that avoids ISL I/O traversing. 

GLYPH<SM590000> Spread multiple host clusters evenly across the FlashSystem 9100 node ports and I/O Groups. 

GLYPH<SM590000> Create one host entity for each host node in FlashSystem 9100 and group them in a hostcluster  entity. 

GLYPH<SM590000> Create separate zones for each host node in FlashSystem 9100 and on the ESX cluster. 

When allocating a LUN/volume to a clustered system, it is highly recommended to use host cluster on FlashSystem 9100, this way you will have your hosts with the same scsi id for every volume, which will avoid outages due to scsi mismatch. 

