Shulou(Shulou.com)06/02 Report--

This section creates a dual-host vSAN cluster (a vSAN cluster with a minimum of 2 hosts)

First, witness the host

In a single-site vSAN cluster environment, we need at least three servers to build a cluster, and a copy of the data is mirrored on two of the servers An and B, respectively, so as to provide highly reliable data protection, so why do we need a third server C?

The Witness is needed to deal with the network failure between servers An and B. if there is a network failure between servers An and B, both servers An and B will try to reorganize the vSAN cluster and compete for shared resources, which may eventually lead to data corruption, which is called a brain fissure. In order to avoid brain fissure, we need a witness (arbitration) role, which is played by server C.

If a brain fissure occurs, vSAN will decide which of servers C, An and B will re-form the new vSAN cluster (2 hosts) based on the vote of the three servers. Because there is data on both An and B, the data will not be lost, and a copy of the data will be replicated on server C after the cluster is reorganized.

In a single-site vSAN cluster, witness roles are randomly assigned, and witness components of virtual machine objects are randomly stored on one of the hosts in the cluster (under RAID1's storage policy).

VSAN supports dual-host cluster architecture since version 6.5. at least two servers are needed to build a complete vSphere/vSAN dual-host environment (called dual-host cluster). The data is mirrored on these two servers, and the role of the witness is assigned to a virtual machine (or ESXi host). The virtual machine or ESXi host is called the witness host, which generally runs in the data center of the enterprise headquarters. Connect to the vSAN dual-host cluster of the branch office through the network and participate in the reorganization decision of the branch vSAN cluster if necessary.

The witness host does not provide specific data services, so the requirement for the wide area network is low. The network connection from the branch office to the data center only needs the bandwidth of 1.5Mbps and the delay of no more than 500ms to meet the communication requirements between the witness host and the vSAN dual host cluster.

The following figure shows a dual-host vSAN cluster in three branch offices connected to a witness host in the headquarters data center.

Witness hosts are currently designed for dual-site VSAN clusters. Conventional multi-node vSAN clusters still use traditional methods, and witness component is scattered across all hosts in the cluster. When the cluster becomes three nodes or more, the new server can bear the responsibility of witness, no longer need to witness the host.

Second, application scenarios

Dual-site vSAN clusters are mainly used in ROBO environments.

ROBO is Remote Office/Branch Office, which refers to a small branch office. For such a small office, two hosts can meet the demand, and three hosts may be a bit wasteful. In this scenario, the witness host is installed on a virtual machine or a dedicated ESXi host in the data center of the head office.

Third, set up a dual-site vSAN cluster

Let's build a two-site cluster using the environment after the last deletion of our single-site cluster. Here we use an ESXi host as the witness host instead of using Witness Appliance.

1. Environment configuration

The host uses the three hosts esxi-vSAN1 esxi-vSAN2 esxi-vSAN3, and adds a 200G hard disk and a 2T hard disk to the esxi-vSAN2 esxi-vSAN3 as vSAN storage.

Esxi-vSAN1, as the witness host, does not add a hard disk for the time being, and its network only retains the bridging network for the time being.

The following figure shows the specific configuration of three virtual machines

Esxi-vSAN1:

Esxi-vSAN2 esxi-vSAN3:

2. Establish a vSphere cluster

(1) New data center, add three hosts to vCenter, then create a new cluster, add 10.8.20.32 and 10.8.20.33 hosts to the cluster, 10.8.20.31 do not join the cluster

(2) add distributed switches for 2 hosts in the cluster

Note that vSAN should be ticked when vmk1 selects a service

Check the vSAN network

3. Enable vSAN service and establish a dual-host vSAN cluster

Enable the vSAN service

Select the second option, dual-host vSAN cluster

Service is not selected for the time being

Declare disk, 200g as cache layer and 2T as capacity layer

To select a witness host, you must select a host that is outside the cluster and cannot be in maintenance mode

Also configure the vSAN network for the witness host

Shut down the host 10.8.20.31, refer to the other two, and add two network cards for it (in a production environment, you can enable vSAN services on the vmk0 where it manages the network)

After adding, turn on the host and add it to the vSAN network

Add 10.8.20.31 hosts to the uplink

Assign uplink

Then add the vmkernel network card and check vSAN

The established distributed switch is as follows

Then exit the host from maintenance mode, and then restart the vSAN service

You can view the requirements of the witness host above

You can see that the witness host also needs a disk group.

The following is to add the disk, according to the configuration of the other 2 sets, add 2 hard drives, a 200G, a 2T (can be added in the boot case).

After adding it, refresh the storage adapter, and you can see the 2 hard drives you added.

Restart the vSAN service

Complete

Wait a moment, the vSAN service has been enabled

4. Test the dual-host vSAN cluster

Create a new virtual machine test01, using the default storage policy

You can see that the witness component of the virtual machine will only be placed on the witness host.

Create a new virtual machine test02 with 2 hard drives, and also use the default storage policy

You can also see that the witness is put on the witness host.

This enables a dual-host vSAN cluster.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.