Tuesday, September 18, 2012

VMware Technical Questions and Answers and Interview FAQ -Part8- Download

71. What is VMotion?

VMware VMotion enables the live migration of running virtual machines from one physical server to another with zero downtime, continuous service availability, and complete transaction integrity. It is transparent to users.

VMotion lets you:

Automatically optimize and allocate entire pools of resources for maximum hardware utilization and availability.
Perform hardware maintenance without any scheduled downtime.
Proactively migrate virtual machines away from failing or underperforming servers.

72.So how Does VMotion work?

First, the entire state of a virtual machine is encapsulated by a set of files stored on shared storage. VMware's clustered Virtual Machine FileSystem (VMFS) allows multiple installations of ESX Server to access the same virtual machine files concurrently.

Second, the active memory and precise execution state of the virtual machine is rapidly transferred over a high speed network. This allows the virtual machine to instantaneously switch from running on the source ESX Server to the destination ESX Server. VMotion keeps the transfer period imperceptible to users by keeping track of on-going memory transactions in a bitmap. Once the entire memory and system state has been copied over to the target ESX Server, VMotion suspends the source virtual machine, copies the bitmap to the target ESX Server, and resumes the virtual machine on the target ESX Server. This entire process takes less than two seconds on a Gigabit Ethernet network.

Third, the networks used by the virtual machine are also virtualized by the underlying ESX Server. This ensures that even after the migration, the virtual machine network identity and network connections are preserved. VMotion manages the virtual MAC address as part of the process. Once the destination machine is activated, VMotion pings the network router to ensure that it is aware of the new physical location of the virtual MAC address. Since the migration of a virtual machine with VMotion preserves the precise execution state, the network identity, and the active network connections, the result is zero downtime and no disruption to users.

73.What is storage Vmotion?

Storage VMotion is similar to VMotion in the sense that "something" related to the VM is moved and there is no downtime to the VM guest and end users. However, with SVMotion the VM Guest stays on the server that it resides on but the virtual disk for that VM is what moves. Thus, you could move a VM guest's virtual disks from one ESX server's local datastore to a shared SAN datastore (or vice versa) with no downtime for the end users of that VM guest.

74.What is the requirement for Vmotion?

Shared Storage Shared VMFS volume
Processor Comapatability

the virtual machine configuration file for ESX Server hosts must reside on a VMFS.

VMotion does not currently support raw or undoable virtual disks or migration of applications clustered using Microsoft Cluster Service (MSCS).

VMotion requires a Gigabit Ethernet network between hosts.

Motion requires a private Gigabit Ethernet migration network between all of the VMotion-enabled managed hosts. When VMotion is enabled on a managed host, configure a unique network identity object for the managed host and connect it to the private migration network.

75. Port used in VCenter Server?

HTTPS – 443 HTTP – 80

Vcenter Diagnostic Port(TCP/IP) – 8083 Vcenter Port(TCP/IP) – 902
Vcenter Heartbeat Port(UDP) – 902
Which version of tomcat used in Vcenter 4?

Its uses Tomcat 6

What port numbers must be open for SRM and VirtualCenter / vCenter Server? VMware VirtualCenter / vCenter Server:

(HTTP)

(HTTPS)

(SSH)

(VMware) 8096 (Tomcat)

VMware Site Recovery Manager:
(HTTP)
8095 (SOAP Listen)

8096 (HTTP Listen)
9007 (API Listen)
9008 (HTTP Listen)

78. Snapshot timeouts and failures.

Virtual machine snapshot deletion can fail for several reasons. However, the removal/deletion is called 'after' the 3rd party backup has completed. If a snapshot removal fails to respond to VC in the expected time, the VC will throw a 'timeout'. This will leave a "ConsolidatedHelper" snapshot on the VM and must be removed before another backup starts.

Possible reasons for snapshot failure.

1) Busy VM I/O
.

Exchange Server, Databases, Domain Controller etc. Microsoft Knowledge Base article 888794 (http://support.microsoft.com/kb/888794)

These VMs do not react well to have their I/O quiesed during snapshotting. Disable LGTO_SYNC driver http://kb.vmware.com/kb/5962168

Install the Microsoft VSS driver http://www.vmware.com/support/vi3/doc/vi3_vcb15_rel_notes.html#vss_quiescing VSS Quiescing Consolidated Backup now uses VSS for quiescing on ESX Server

3.5 Update 2 hosts when backing up Windows Server 2003, Vista, and Windows Server 2008 virtual machines. To use this feature, VSS components must be installed on the virtual machine as part of updated VMware Tools. The VSS components in the tools perform application-level quiescing on Windows Server 2003 and file system-level quiescing on Windows Vista and Windows Server 2008 virtual machines.

Consolidated Backup continues to uses SYNC driver for quiescing on pre-ESX Server 3.5 Update 2 hosts.

2) Space on volume.

If a snapshot has grow too large during the backup, it can fail to remove because extra space is needed on removing 'layered' snapshots. This can happen if there is existing snapshots prior to another backup call.

3) Busy vmfs volumes.

If several Vms on the same volume are trying to remove their snapshots at the same time, then 'reservation' conflicts can occur and halt the removal. VMware backup recommendations suggest staggering VM backup schedules to avoid to many snapshots on the same luns.

4) Service Console Busy

If the mgmt services memory on the ESX server is low, this can inhibit the snapshot removal process and either fail the removal or cause a long delay resulting in the timeout response from VC.

i)You can increase the Service Console memory to 800MB. Requires reboot. http://kb.vmware.com/kb/1003501

ii)You can increase the VC timeout to 600. Edit>Client Settings. Use Custom Value seconds 600
http://kb.vmware.com/kb/1004790

5) SAN latency issues


If luns are not responding or scsi commands are slow to reply, the ESX may fail to snapshot removal.

6) Scripted

Customized scripts that do not allow for scheduling, multiple vmfs
snapshotting, or deletion. Edit the Remote Command Timeout in Client>Setting on the VC GUI to 600.

I would not quickly dismiss using VCB, as it is only a backup enabler. If any solution, be it manual or 3rd party leverages the ESX Snapshot
mechanism, it has to concede/conform to the known snapshoting limitations.
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