Question

How to identify targets, devices and routes in VMware

Answer 1

Concepts

Connected Targets: are the Ports of each SP that has a LUN presented. The ID of the Target will depend on the order in which the PSA service makes the discovery. In iSCSI, when we have multipath, every connection from a PortGroup (VMKernel with VMNic) to an SP will count as a connected Target.
Devices: It is the number of LUNs to which we have access. Regardless of the Targets and Paths.
Paths: It is the number of Routes available that we have to access the Devices.
SP: Storage system controller. Normally the SAN / NAS systems of medium / high range have two SP.
Runtime Name: represents the path (s) to access the LUNs. They use the format vmhbaX, Channel Y, TargetZ, LUNXX Example: vmhba33: C1: T1: L0
VMHBA: is the name of storage adapters with which we will access storage devices. Physical adapters use names like vmhba 2 or vmhba3, and iSCSI adapters (both Software and Hardware) use a higher number such as 33, 34 or 35.
In Hosts with iSCSI initiators by Software, a single Adapter is created, even though we have several VMKernel added as bindings.
Channel: identifies the channel number used to access storage. In FC it is zero, in iSCSI it can be 0 or 1.
Target: as discussed above are the connections to the ports of each controller of the storage system.
LUN: finally identifies the ID of each connected LUN.

Types of Connections

We will show some connections to a Storage System by altering the number of VMNics and LUNs to see how the values ​​are changing. In all cases we will use an iSCSI connection by Software. The cabin has two controllers, SPA and SPB. In these examples we will use a single Ethernet interface for each SP.

The configuration of Network in the Hosts is composed of two vSwitches with a PortGroup of VMKernel and a VMNic each as shown in the image below.

Concexion 1: iSCSI initiator with a single Binding to a cabin with a single LUN presented.

In this case we see that there is a Target connected, with a LUN presented in SPB and a single route. We see that you have identified the Target SPB of the cabin as Target 1 and the first PortGroup as C0.

Connection 2: We enable Multipath.

We add an additional Binding so that the iSCSI initiator can work with two VMKernels (each with its VMNic). We can see that the new PortGroup adds an additional route of access to the LUN by having two access routes, but always accessing through the same Target 1 (SPB of the cabin). Having added the additional PortGroup we see that we have an additional Channel, C1 and C0.

Connection 3: We will publish a new LUN using the same Target.
By publishing it in the same Target (SPB of the Cabin) we keep identical number of Targets connected, an additional Device that is not more than the LUN that we just created, and now the routes are 4. The number of routes has been increased up to 4 because there are two routes for each Device, being able to see four active routes and two with I / O operations. We are using the two PortGroups (Channel 0 and Channel 1) and connected to a single Target, identified as T1 (SPB).

With these concepts we can understand the targets, devices and vmware routes. So we can connect our types of storage.

Ricardo Quagliano

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