Information Technology Reference
In-Depth Information
Is There a Fibre Channel Equivalent to VLANs?
Actually, yes, there is. Virtual storage area networks (VSANs) were adopted as a standard in 2004.
Like VLANs, VSANs provide isolation between multiple logical SANs that exist on a common physi-
cal platform. h is enables SAN administrators greater fl exibility and another layer of separation
in addition to zoning. h ese are not to be confused with VMware's new VSAN feature described
earlier in this chapter.
Zoning is used for the following two purposes:
To ensure that a LUN that is required to be visible to multiple hosts in a cluster (for example
in a vSphere cluster, a Microsoft cluster, or an Oracle RAC cluster) has common visibility to
the underlying LUN while ensuring that hosts that should
not
have visibility to that LUN
do not. For example, it's used to ensure that VMFS volumes aren't visible to Windows serv-
ers (with the exception of backup proxy servers using software that leverages the vSphere
Storage APIs for Data Protection).
◆
To create fault and error domains on the SAN fabric, where noise, chatter, and errors are
not transmitted to all the initiators/targets attached to the switch. Again, it's somewhat
analogous to one of the uses of VLANs to partition very dense Ethernet switches into
broadcast domains.
◆
Zoning is coni gured on the Fibre Channel switches via simple GUIs or CLI tools and can be
coni gured by port or by WWN:
Using port-based zoning, you would zone by coni guring your Fibre Channel switch to
“put port 5 and port 10 into a zone that we'll call zone_5_10.” Any device (and therefore
any WWN) you physically plug into port 5 could communicate only to a device (or WWN)
physically plugged into port 10.
◆
Using WWN-based zoning, you would zone by coni guring your Fibre Channel switch
to “put WWN from this HBA and these array port WWNs into a zone we'll call ESXi_55_
host1_CX_SPA_0.” In this case, if you moved the cables, the zones would move to the ports
with the matching WWNs.
◆
The ESXi coni guration shown in Figure 6.9 shows the LUN by its runtime or “shorthand”
name. Masked behind this name is an unbelievably long name that that combines the initiator
WWN, the Fibre Channel switch ports, and the Network Address Authority (NAA) identii er.
This provides an explicit name that uniquely identii es not only the storage device but also the
full end-to-end path.
We'll give you more details on storage object naming later in this chapter, in the sidebar titled
“What Is All the Stuff in the Storage Device Details List?”
Zoning should not be confused with LUN masking.
Masking
is the ability of a host or an
array to intentionally ignore WWNs that it
can
actively see (in other words, that are zoned to it).
Masking is used to further limit what LUNs are presented to a host (commonly used with test
and development replicas of LUNs).
You can put many initiators and targets into a zone and group zones together, as illustrated
in Figure 6.10. For features like vSphere HA and vSphere DRS, ESXi hosts must have shared
