6.7

Using Zoning with Fibre Channel SANs
Zoning provides access control in the SAN topology. Zoning defines which HBAs can connect to which
targets. When you configure a SAN by using zoning, the devices outside a zone are not visible to the
devices inside the zone.
Zoning has the following effects:
n
Reduces the number of targets and LUNs presented to a host.
n
Controls and isolates paths in a fabric.
n
Can prevent non-ESXi systems from accessing a particular storage system, and from possibly
destroying VMFS data.
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Can be used to separate different environments, for example, a test from a production environment.
With ESXi hosts, use a single-initiator zoning or a single-initiator-single-target zoning. The latter is a
preferred zoning practice. Using the more restrictive zoning prevents problems and misconfigurations that
can occur on the SAN.
For detailed instructions and best zoning practices, contact storage array or switch vendors.
How Virtual Machines Access Data on a Fibre Channel
SAN
ESXi stores a virtual machine's disk files within a VMFS datastore that resides on a SAN storage device.
When virtual machine guest operating systems send SCSI commands to their virtual disks, the SCSI
virtualization layer translates these commands to VMFS file operations.
When a virtual machine interacts with its virtual disk stored on a SAN, the following process takes place:
1 When the guest operating system in a virtual machine reads or writes to a SCSI disk, it sends SCSI
commands to the virtual disk.
2 Device drivers in the virtual machine’s operating system communicate with the virtual SCSI
controllers.
3 The virtual SCSI controller forwards the command to the VMkernel.
4 The VMkernel performs the following tasks.
a Locates the appropriate virtual disk file in the VMFS volume.
b Maps the requests for the blocks on the virtual disk to blocks on the appropriate physical device.
c Sends the modified I/O request from the device driver in the VMkernel to the physical HBA.
5 The physical HBA performs the following tasks.
a Packages the I/O request according to the rules of the FC protocol.
b Transmits the request to the SAN.
vSphere Storage
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