VSP3867 Top 10 Virtualization Support Issues

VSP3867Top 10 Virtualization Support Issues

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Top 10 Support Issues

“An ounce of prevention is worth a pound of cure!”

• Identify the most common topics our customers engage us with.• Anticipate the potential problems you may encounter.

• Prepare an action plan to address these problems.

• Become informed on the most frequent support topics before you encounter them.

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VMotion CPU Compatibility

• Problem:• CPUs need to preferably be identical for certain operations such as FT and VMotion.

If they are not, compatibility warnings are shown or the operations may not be possible

• Symptoms:• CPU Compatibility messages

• Virtual machine failures or crashes

• Recommendations:• Do NOT use CPU masking. USE Enhanced VMotion Compatibility (EVC)

• Buy servers in bunches (3 to 4 or more) that all are identical.• Keep AMD and Intel servers in different clusters

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Top 10 Support Issues (2)

vCenter Database size• Problem:

• The size of the vCenter database grows very large.

• Symptoms:• Database files / Transaction logs grow large

• Deadlocks occur when processing performance data

• Recommendations:• Most database size problems occur due to statistic or Task/Event information

• Check that the agent service is running or performance data will not be processed• Check that adequate RAM and CPUs exist on the SQL Server• Perform regular database maintenance such as backups and defragmentation of the

indexes

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vCenter shows high Memory utilization in vCenter 4• Problem:

• Newer processors that have built in virtualization support and can utilize large pages show what appears to be large memory usage of the VMs and ESX.

• Resolution:• None, there is no problem here!

• Large Pages provide a performance increase of ~25% on heavy workloads such as SQL Databases

• Memory usage shown is actually consumed memory and should not be used as the only indicator of memory utilization.• If memory usage is never above 80% than vSphere features such as over

commitment ballooning and transparent page sharing will never be used

• Look at swap-in/swap-out, and active memory to get a better view of the memory utilization taking virtualization overhead into account.

• Disabling large pages will move the behavior back to pre vCenter 4 views, but the benefits of having them enabled out weigh the drawbacks. VMware does not recommend disabling Large Pages.

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VMware HA Configuration fails• Problem:

• Commonly HA will sometimes fail with “ HA Agent has an error”

• Recommendations: • Make sure that the ESX Servers are able to ping each other and the configured

default gateway or configuration will fail

• Most common problems configuring HA are in the following categories:

• DNS Name Resolution• Networking Configuration• Time Configuration

• For further troubleshooting regarding VMware HA, see Troubleshooting VMware High Availability (HA) (1001596)

http://kb.vmware.com/kb/1001596

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vCenter / ESX Upgrade issues• Problem:

• Upgrades of vCenter sometimes are not as easy as pointing and clicking. A lot of cases are not problems but an issue where best practices are not followed.

• Recommendations:• Most of the problems seen can be avoided by

• Ensuring that there are enough resources available, most importantly disk space

• Ensure that the database revision is still supported (SQL 2000 is not in vSphere 4)• BACKUP BACKUP BACKUP the vCenter database• Permissions on the vCenter Database and the MSDB

• Make sure the host is 64-bit, as it is a requirement for ESX4.

• Detach the SAN for ESX Upgrades to local disks, otherwise make sure to install to the proper LUN

• Always follow the practices in Upgrading to ESX 4.0 and vCenter 4.0 best practices (1009039)




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ESX Servers show not responding in vCenter• Problem:

• ESX Hosts may show not responding in vCenter and customers will reboot the host rather than troubleshooting.

• In the most general of terms this will happen for two reasons:

• Network problems (including ESX Firewall)

• ESX Management service problems

• Recommendations:• If Console login is possible, then many times a whole host reboot can be avoided.• Review the ESX Host Logs vpxa.log, hostd.log and vmkernel.log for clues as to what

is happening

• Look out for:

• storage errors (most common reason for hostd service issues)• Service console available memory / CPU• Third party interaction (SDK, etc.)

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Snapshots!• Many misconceptions of snapshots function

• Snapshots are meant for point in time restores, while doing maintenance in the VM• Not meant to be kept for long periods of time

• Data is not stored in the VMDK, rather in a sparse outside the allocated disk space

• There are a multitude of snapshot related issues:• Using them as backups

• Nested snapshot trees• Corruption of snapshot tree due to inadvertently powering on the base disk

• Recommendations• Whenever adding an existing disk to a new virtual machine make sure you are not

adding a parent disk. (GUI does not display snapshots!)

• Use a proper product such as VCB to do your backups. This will prevent large nested snapshot trees and use the technology properly.

• If you are using them make sure adequate space is available on the LUN

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All Paths Down (APD) state disrupts virtual machines on unrelated LUNs• Issue:

• During an APD condition the ESX Storage layer retries I/Os to VMFS datastores.

• Rescan operations take a long time.

• Symptoms:• Virtual machines on unaffected LUNs appear to be unresponsive.

• Workaround/Resolutions• Mask the LUNs in question. Follow the instructions in

Unpresenting a LUN containing a datastore from ESX 4.x and ESXi 4.x (1015084)

• VMware has fixed the problem in ESX4.0 P3 ( ESX400-200912001 on the download site)







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Cannot connect to View Desktop• Problem:

• Client cannot properly connect to the View connection server

• Symptom:• Generic error messages saying “Cannot Connect to Desktop”

• Resolutions:• External configuration issues are the normal cause for this when connecting to a

desktop fails

• Network configuration

• Firewalls• Incorrect version of the View client, agent, and/or connection server. Verify the version

is appropriately matched.

• Collect the View log files and validate if there is any more specific error message to indicate a problem in the logs. For more information , see Collecting diagnostic information for VMware View 3.x and 4.0.x (1017939)


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PCoIP Multi-Monitor configurations with Windows 7 in View v4.0.x• Problem:

• Both screens may not be detected or may flicker a lot before it stabilizes

• Resolution:• Officially this is an unsupported experimental configuration with View 4.0.x .

• Full support has been added in View v4.5.x and newer versions. Updating will allow this functionality.

• Workarounds:• To get it to work, add more Video RAM to the virtual machine (bigger multiples of 64

are better) will sometimes resolve the problem• Confirm that the VMX file properly is configured to use two monitors• Editing the default resolution and monitor configuration in the settings of the desktop

pool within View.

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Summary

Each of these problem areas could be encountered in your own infrastructure.

Identifying the most common problems allows you to anticipate them and develop a plan to prevent these issues before they occur.

Stay up to date with software patches and updates. Be sure to read the release notes and understand what issues are addressed in each release.

VSP3867 Top 10 Virtualization Support Issues

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