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Using Fibre Channel with ESX/ESXi
Fibre Channel SAN LUNS:
- Used for VMFS datastores to hold virtual machines, ISO images, and templates
- Used for holding RDMs, which point to a virtual machine’s raw data
- Used for remote booting of ESX/ESXi
- Support vSphere features like vMotion, VMware HA, and DRS
ESX/ESXi supports:
- 8Gb Fibre Channel
- Fibre Channel over Ethernet (FCoE)
Fibre Channel SAN Components
A Fibre Channel SAN consists of:
- Storage system – The hardware that consists of a set of physical hard disks, or disk array, and one or more intelligent controllers. The storage system supports the creation of LUNs. The SPs of disk arrays aggregate physical disks into logical volumes, or LUNS, each with a LUN number identifier.
- LUN – The address of a logical unit (LU). An LU is a unit of storage access. An LU can be a JBOD (just a bunch of disks) or a part of a JBOD, a RAID set or part of a storage container. Both a JBOD and a storage container can be partitioned into multiple LUNs. An LU can also be a control function like an array gatekeeper LUN or tape controller.
- Storage processor – An SP can partition a JBOD or RAID set into one or more LUNs. It can restrict access of a particular LUN to one or more server connections. Each connection is referenced by the server HBA’s WWN. An SP might also require defining the operating system in the connection tables to adjust how the storage array controller presents Fibre Channel and SCSI commands to a particular server.
- HBA – Connects the ESX/ESXi host to the Fibre Channel network. It is required, along with cables attached to the FIbre Channel switch ports. A minimum of two HBA adapters are used for fault-tolerant configurations. Virtual machines see standard SCSI connections and are not aware of the underlying SAN being accessed.
- Fibre Channel switches – One or more Fibre Channel switches form the Fibre Channel fabric. The Fibre Channel fabric interconnects multiple nodes. The Fibre Channel switches form packets from the Fibre Channel messages and add the source and destination addresses to each packet. The Fibre Channel switch might have to be updated by flash upgrade to firmware to resolve interoperability issues and to add new features.
Fibre Channel Addressing and Access Control
Several mechanisms enable controlling host’s access to LUNs. Soft zoning, which is done on a Fibre Channel switch, controls LUN visibility per WWN. The Fibre Channel switch might also implements hard zoning, which is the control of SP visibility per switch port. Fabric zoning controls target presentation and tells an ESX/ESXi host whether a target exists. If the host cannot get to the target, then it cannot see the LUNs. In many well-managed SAN environments, both soft and hard zoning are in use. The purpose of using both is to make accidental access to volumes by servers very unlikely.
Zoning is especially important in environments where physical Windows servers are accessing the SAN, because Windows operating systems typically write a disk signature on storage volumes that they can see. These volumes might be in uses by non-Windows systems.
WWNs are assigned by the manufacturer of the SAN equipment. HBAs and SPs have WWNs. WWNs are used by SAN administrators to identify your equipment for zoning purposes.
The SP or hosts themselves might also implement LUN masking, which controls LUN visibility per host. An ESX/ESXi host offers a mechanism for LUN masking. Although LUN masking can be done in the ESX/ESXi host, LUN masking is normally done at the SP level for the sake of security and data integrity. With newer switches, LUN masking can also be done at a switch or fabric level. If a LUN is masked, the SP does not tell the host that the LUN exists, nor does the SP allow communication with the LUN.
Accessing Fibre Channel Storage
By default, the VMkernel scans for LUNs 0-255 for every target ( a total of 256 LUNs). You cannot discover LUNs with a LUN ID number that is greater than 255.
To display a list of storage adapters, select your host in the inventory and click the Configuration tab. Click the Storage Adapters link.
Viewing Fibre Channel Storage Information
The Storage Views tab provides information about all SCSI adapters and NAS mounts.
In the vSphere Client, the Storage Views tab allows you to review associations between all storage entities available in VMware vCenter Server and analyze storage usage. The storage usage data appears as reports and storage topology maps on the Storage Views tab. Use the Reports view to analyze storage space and availability, multipathing status, and other storage properties of the selected object and items related to it.
Use the Storage Views tab to view information about your FIbre Channel storage. You can also view the relationship between various entities and storage, such as:
- Datastore to virtual machine or host
- Virtual machine, host, or cluster to datastore
- Virtual machine to SCSI volume, path, adapter, or target
The reports are searchable. You can select which pieces of information to display by right-clicking the header bar of the report and selecting the desired column headings.
Reports are updated every 30 minutes. Click Update link to manually update reports.
Viewing Fibre Channel Storage Maps
Storages are an easy way to visually represent relationships between selected inventory objects and storage. For example, you can view what targets a virtual machine can see or how many paths a virtual machine has to a storage device. Maps can assist in troubleshooting by showing problem entities.