Vmware terminology

- 1- In vmware they use the following terms:
High Availability

 how they are different?

2- when VM machine needs more resources that can not be provided by the current ESX server, then it moves to another ESX server.
 in this case, I believe the VM machine doesn't reboot in order to move from one ESX to another. How does this operation called? HA or Vmotion or DRS?

-3- when an ESX server that is servicing multiple VMachines fail, the vmachines will move to another ESX server. Would these vmachines reboot before they move to the ESX server? how do we call this operation vmotion,DRS,HA?

Assuming of course there is SAN storage implementation


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ceesiosConnect With a Mentor Commented:
High Availability is a system that restarts vm's if they fail either because of a host (ESXi) failure of because the vm crashes (if you are monitoring for this). This all works automaticaly if it's configured. If you want machines to stay online in case of a host failure you would use Fault Tollerance witch wil effectivly keep a synchronized copy running of the entire vm on a second host so you don't have any downtime.

vMotion is used to migrate a virtual machine from one host (ESXi) to another in an cluster. This is usually used to perform maintanance of by DRS. It can be done live of with the vm powerd off. You can also use vmotion to move the storage somewhere else (anohter lun, local e.d.)

Destributed Resource Scheduling makes sure the load is evenly spread over the available capacity in the cluster by moving vm's around with vMotion. It can also work in combination with Distributed Power Management to turn on and off hosts as there resources are needed.
Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
Question 1.

Explain the Terms HA, DRS, vMotion

HA -  high availability

Key Features

    * Automatic detection of server failures. VMware HA automates the monitoring of physical server availability.  HA detects physical server failures and initiates the new virtual machine restart on a different physical server in the resource pool without human intervention.
    * Automatic detection of operating system failures.  VMware HA detects operating system failures within virtual machines by monitoring heartbeat information. If a failure is detected, the affected virtual machine is automatically restarted on the server.
    * Smart failover of virtual machines to servers with best available resources (requires VMware DRS). Automate the optimal placement of virtual machines restarted after server failure.
    * Scalable high availability across multiple physical servers.  Supports up to 32 nodes in a cluster for high application availability. VMware HA has the same limits for virtual machines per host, hosts per cluster, and virtual machines per cluster as vSphere.
    * Resource checks. Ensure that capacity is always available in order to restart all virtual machines affected by server failure. HA continuously and intelligently monitors capacity utilization and reserves spare capacity to be able to restart virtual machines.
    * Proactive monitoring and health checks.  VMware HA helps VMware vSphere users identify abnormal configuration settings detected within HA clusters. The VMware vSphere client interface reports relevant health status and potential error conditions and suggested remediation steps. The Cluster Operational Status window displays information about the current VMware HA operational status, including the specific status and errors for each host in the VMware HA cluster.
    * Enhanced isolation address response. Ensures reliability in confirming network failure by allowing multiple addresses to be pinged before declaring that a node is isolated in the cluster.



DRS - Distributed Resource Scheduler  

# Aggregation of physical server resources.  Manage CPU and memory across a group of  physical servers as a uniform shared pool of resources.
# Flexible hierarchical organization.  Organize resource pools hierarchically to match available IT resources to the business organization. VMware DRS ensures that resource utilization is maximized while business units retain control and autonomy of their infrastructure. Resource pools can be flexibly added, removed, or reorganized as business needs or organization change.
# Priority Settings. Assign priorities in the form of shares or reservations  to virtual machines within resource pools and to sub resource pools to reflect business priorities. For example, the production sub resource pool can have higher shares of the total resources in a cluster and business critical applications within the production resource pool can have fixed guarantees(reservations) of CPU bandwidth and memory,
# Management of sets of virtual machines running a distributed application.  Optimize the service level of distributed applications by controlling the aggregate allocation of resources for the entire set of virtual machines running the distributed application.
# Affinity Rules. Create rules that govern placement of virtual machines on physical servers. For example, a group of virtual machines can be set to always run on the same server for performance reasons. Alternatively, certain virtual machines can be set to always run on different servers to increase availability. New in vSphere 4.1 is the ability to restrict placement of virtual machines to a group of physical servers in a cluster. This is useful for controlling the mobility of virtual machines that run software licensed for a specific group of physical servers. In addition, this feature can be used to keep sets of virtual machines on different racks or blade systems for availability reasons.
# Power Management. Reduce energy consumption in the datacenter by using the Distributed Power Management (DPM) feature of DRS to consolidate workloads and power off servers when they are not needed by the virtual machines in the cluster. When resource requirements of virtual machines increase, DPM brings hosts back online so service levels can be met.
# Manual and Automatic Mode.   VMware DRS collects resource usage information from servers and virtual machines, and then generates recommendations to optimize virtual machine allocation. These recommendations can be executed automatically or manually.

    * Initial placement.  When a virtual machine is first powered on, VMware DRS either automatically places the virtual machine on the most appropriate physical server or makes a recommendation.
    * Continuous optimization. VMware DRS continuously optimizes resource allocations based on defined resource allocation rules and resource utilization. The resource allocation changes can be automatically executed by performing live migration of virtual machines through vMotion. Alternatively, in manual mode, VMware DRS provides execution recommendations for system administrators.

# Maintenance mode for servers.  Perform maintenance on physical servers without disruption to virtual machines and end users. When a physical server is placed in maintenance mode, VMware DRS identifies alternative servers where the virtual machines can run. Based on automation mode settings, the virtual machines are either automatically moved to use the alternative servers, or the system administrator performs the move manually using the VMware DRS recommendations as a guideline.
# Large-scale management. Manage CPU and memory across up to 32 servers and 1280 virtual machines per DRS cluster.




Perform live migrations with zero downtime to the end-users.  Optimal use of CPU and network resources ensures that the live migrations occur quickly and efficiently. Performance (up to 5X) and scale improvements (move up to 8 VMs at a time) with 4.1.



Question 2.

If a Virtual Server is seen to be using more resources, and it woould be better distributed to an ESX Host, which has more resources available, DRS in a Cluster is used, but it's dependant upon vMotion to Live Migrate the VM.

Question 3

If an ESX Host fails, ALL the VMs on that host also fail. But with HA, they are started immediately on other hosts in the farm. So there are a few minutes of downtime.

But I'm going to throw in another technology for you also to consider



VMware Fault Tolerance provides continuous availability for applications in the event of server failures,  by creating a live shadow instance of a virtual machine that is in virtual lockstep with the primary instance. By allowing instantaneous failover between the two instances in the event of hardware failure, VMware Fault Tolerance eliminates even the smallest chance of data loss or disruption.

jskfanAuthor Commented:
thanks guys
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