Vmware Fault Tolerance (FT)

Fault Tolerance

Vmware FT provides zero downtime and continuous availability of virtual machines in case of host failure.

This is achieve by creating 'Live Shadow' copy of the running virtual machine and using new fast check-pointing mechanism to keep the primary and the secondary virtual machines in sync.

                                                                                                                          grpahics by vmware

If an ESX Server fails the shadow will take over and a new shadow will be created in the cluster on other ESX Server. The secondary virtual machine is a completely separate including storage for the first time and can now be on a different datastore from the primary.

Its takes the VMHA to the next level, works for all application and most of the guest operating system supports F.T.

Requirement of F.T

• CPU's must Support F.T (check vmware official cpu compatibility list)
• Vmkernel interface on both ESXi host with F.T enabled.
• Host must be in a HA cluster.
• Recommended NIC's of 10 Gig for F.T
• VM's on shared SAN and accessible by server
• vSphere standard, Enterprise and Enterprise Plus  any of these licence.

Vmware DRS (Distributed Resource Scheduler)

DRS -Distributed Resource Scheduler

Vmware DRS cluster is a collection of multiple ESXi hosts and virtual machines with shared resources.

When you add host in DRS cluster, the host resource becomes part of cluster resource.

Following are the DRS capabilities.

Load Balancing

Auto load balancing of virtual machines with respect to CPU and memory utilization across ESXi host within cluster. DRS monitors the resource utilization and moves the virtual machines to another host where it gets the ideal resource. Its uses vmotion technology and its plan vmotion of virtual machines.

Power Management

Distributed Power Management (DPM), if enable in cluster its power off the ESXi host server when its in ideal state while during peak hours whenever cluster requires more resource its power ON the server. we can say its saves power by shutting down the physical (ESXi host) server. Its might uses vmotion to migrate the virtual machines to other hosts.

Virtual Machines Placement

DRS comes with affinity(together) and Anti-affinity(Separate) rules for placement of redundant and dependent virtual machines as needed.

Benefits of DRS

• Auto load balancing of virtual machines that mean no need to manually initiate vmotion.
• Prevents virtual machines from monopolizing all resources
• Offers most efficient user of server hardware.
• you can create migration rules to keep virtual machines together or apart.
• DRS can auto place new virtual machine in the cluster.

Requirement of DRS

• vShpere Enterprise or Enterprise Plus licence.
• Shared storage between hosts.
• All virtual machines in the cluster must be on that shared storage.
• DRS uses the vmotion so its needs to work between hosts CPU's to avoid compatibility issues checkout the Enhanced Vmotion Compatibility (EVC).

Vmware High Availibility

Vmware HA (VMHA)

In case of host failure all virtual machines running on dead ESXi host will be restarted on another ESXi host within the cluster.

HA Downtime is equal to Reboot time.

How does VMHA works ?

VMware HA continuously monitors not only ESXi host failure but also Guest OS failures in a cluster. Its install a agent on each host while placing it inside HA cluster a heartbeat with the other host in the cluster and loss of a heartbeat initiates the process of restarting all affected virtual machines on other hosts.

Uniform HA protection for all virtual machines and application no matters the OS or application support and admission control ensures that resources are available on host machines for CPU and RAM reservation while failure.

Requirement for VMHA

• Shared Storage for virtual machines running in HA cluster.
• Can use advance feature like DRS with VMHA or just VMHA only.
• vShpere Essential Plus, Standard, Enterprise, Enterprise Plus any of these licence
• At least two host in the cluster.
• Create a VMHA enabled cluster.

VMHA Master / Slave (FDMS)

• Master host per cluster known as the Fault Domain Manager Master (FDMS).
• FDMS host is determined via an election process.
• FDMS host with most mounted datastore has better election chances.
• VMHA checks per host failure using the management network and via datastore heartbeat.

Roles of FDMS host

• Monitors the state of slave hosts.
• Monitors the state of all protected virtual machines.
• Manages the list of cluster hosts and protected virtual machines.
• FDMS is vCenter management interface into the cluster health state.

What is ESXi, vCenter and vShpere Client

ESXi Server

Its a type 1 Hypervisor also know as Bare metal hypervisor developed by vmware.

ESXi directly installs in your physical server which enables you to create multiple virtual machines, you can use ESXi with either the free vShpere hypervisor without some additional features or the paid edition of vSphere hypervisor.

Difference between ESX and ESXi

After version 4.1 vmware renamed ESX to ESXi  and replace service console with DCUI (direct control user interface) some of the major benefits are follows:

vCenter Server

vCenter Server previously know as vmware virtual center some of the benefits are as follows

• Its used for centralized control and visibility of multiple ESX/ESXi hosts.
• Contains centralized license management.
•  Provides most advance features of vmware vshpere like vmotion etc.

Pre-requisites for installing vCenter version 6

Software requirement: Wnidows 2008 R2 64 bit or later and should not be a domain controller.

Hardware requirement: Dual-Core 64 bit processor with minimum 8GB of RAM. 

vShpere Client

vShpere client is used to access ESXi host or vCenter server the diagram below gives descriptive idea of vsphere suits.

Graphics thanks to vmware

This covers the working of VShpere suit as we can observe there is one physical server installed with ESXi server running virtual machines and sharing the resources like CPU and memory from host server (physical).

vCenter itself installed in vm in windows server, we can also use VCSA (vCenter Server appliance) linux based vCenter pre-installed with vCenter or we can have dedicated physical server. Best practise is to have it on vm if there any issues in physical server or its require down time maintenance in some activity so we can migrate the vCenter to another ESXi server so its doesn't impact on daily operation. To access this vcenter we require a client machine can be a laptop or desktop with vSphere client installed in it, from vShpere client we can access vcenter server and ESXi server by simply providing a IP address and login credentials. In big environment with multiple ESXi hosts an dozens of vm its highly recommended to have at-least one vCenter server its makes easier to manage ESXi hosts and vms, templates no need to login on each ESXi server and alos its comes with additional features like vmotion, DVSwitch, etc which makes the daily activity of vmware admin easier.

What is vmware vSphere ?

Vmware vShpere

Don't be confused between vmware and vShpere, Vmware is a application making cpmpany (or vendor) who develops a product for datacenter, cloud and workstation virtualization.

vShpere

Its a suit of application product which contains ESXi (a Hypervisor), Vcenter, Vshpere client software and its developed by vmware. Hence its a server virtualization platform previously it was known as virtual infrastructure.

Physical topology of vShpere Datacenter

Graphics thanks to vmware

In depth explanation about Vshpere suit related products which is listed above are available in next blog link available below.

http://techequest.blogspot.com/2017/01/what-is-esxi-vcenter-and-vshpere-client.html

What is Storage Vmotion or SVmotion ?

What is Storage Vmotion

Storage Vmotion (sVmotion ) its a  migration of running virtual machine's storage from one datastore to another with zero downtime and virtual machine will remain in the same host.

Benefits from Storage vmotion

1. Balance the datastoe utilization.
2. Perform SAN maintenance by moving storage from one SAN to another or swap out
3. Move local ESXi storage to SAN storage

Requirement for Storage vmotion

1. Licencing- required standard, enterprise or enterprise plus only.
2. All storage need to be accessible to the ESXi server where the VM is running
3. This works- local to SAN or SAN to local
4. Don't works- local of ESXi-1 to local of ESXi-2 (Exception is shared nothing live migration)
5. Moving of powered on VM with snapshot is not supported till version-4
6. Note that to use the option to change both host and datastore, the VM must be powered off till version-5
7. Moving a large VMDK can take a long time, depending on your network connection.

What is Vmotion ?, Why you need Vmotion?, Requirement of Vmotion ?

What is Vmotion

Vmotion is a feature available in vCenter Server, which allows you to live migrate virtual machine from one ESXi host to another with zero application downtime.

Why you need Vmotion benefits and uses

1. Can move running virtual machine from one ESXi server to another ESXi server.
2. The VM's disk file stay where they are (on shared storage).
3. Balance the load on ESXi server with respect to CPU and memory utilization.
4. Perform patching and maintenance on an ESXi server.

Vmotion requirement

1. Fist thing you require is the licence vSphere Essential plus, standard, enterprise or enterprise plus at least on of these license.
2. Shared storage between ESXi servers iSCSI,FC or NFS if not then now shared nothing live migration is possible.
3. Vmkernel interface on both the ESXi servers with VMotion enabled.
4. Works with standard switch or distributed switch (should keep the same network name).
5. EVC- enhanced Vmotion compatibility should on in your cluster for CPU compatibility or family compatibility if there are different types of CPU available inside cluster.

We try to simplify the things in this blog. Please leave a comment and suggestion regarding this topics. Thanks for reading.

VMFS Block Size Explained

What is Block Size ?

The Block Size determines the minimum amount of disk space that any file will takes up on VMFS datastore.

The block size also determines the maximum size that any file can be, if you select a 1 MB Block Size on your data store the maximum file size limited to 256 GB.

Table illustrate different VMFS version Block Size.

VMFS-3 Block Size

VMFS-5 Block Size is less complex 😊






To Check the block size of Datastore.

From ESX Console

1. Log in to ESX using PUTTY
2. Run the command: # vmkfstools -P <path to datastore>

Where 1048576 is equivalent to  1 BM block size on a VMFS datastore.


From the vSphere Client:

1.Select an ESX host that contains the datastore
2.Click the Configuration tab.
3.Click Storage.
4.Select the datastore.
5.The block size is mentioned below Datastore details windows

Note: There is no way to change the block size of a VMFS datastore once it is created. The data store must be deleted, recreated and reformatted with the required Block Size.