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VMWare Fiber Channel

The Basics


Is done at the Fiber Channel switch (soft and hard) or at the Storage Processor (SP) and controls LUNs visibility per WWN. Fabric zoning (hard zoning) controls target presentation and tells an host whether a target exists. If the host cannot get to the target then it cannot see the LUNs.
Soft zoning: LUN visibility Hard zoning/fabric zoning: target visibility (the entire SP, required when using multiple SPs/SANs)
Zoning is especially important in environments where physical Windows Servers are accessing the SAN, because Windows typically writes a disk signature on storage volumes that they see, even if they're not using them.


LUN masking is done at the Storage Processor or at the server level. It makes a LUN invisible when a target is scanned. With newer Fiber Channel switches, LUN masking can also be done at the switch level. For sake of security, it is mostly implemented at SP level.

WWNs - World Wide Name

WWNs are assigned by manufacturers to SAN equipment. They are used for identifying equipment for zoning purposes.

Fiber Channel Load Balancing

Within VMware it is possible to select different path policies for Fiber Channel targets. This is done for scalability and availability purposes:


Fixed is when the host always used the preferred path to the disk as long as the path is available. If the path fails, alternative paths are tries. This is the default policy for active-active storage devices.

MRU - Most Recently Used

With MRU the most recent path to the disk is used until this path becomes unavailable. It does not revert back to the preferred path. MRU is the default policy for active-passive storage devices and is required for those devices.

Round Robin

A path selection algorithm that rotates through all available paths. Besides path failover the round robin policy supports load balancing across the paths.

Note: Round Robin is not supported on all storage, so check with your vendor whether this policy is supported.

Set the Policy

Go to the datastore properties → Manage Paths and select a policy from the path selection drop-down menu.

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vmwarefiber.txt · Last modified: 2013/04/20 13:51 by sjoerd