Category Archives: Virtualisation

VCAP-DCA Study guide – 6.5 Troubleshoot vCenter Server and ESX/ESXi Host Management

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Knowledge

  • Identify CLI commands and tools used to troubleshoot management issues

Skills and Abilities

  • Troubleshoot vCenter Server service and database connection issues
  • Troubleshoot the ESX Service Console firewall
  • Troubleshoot ESX/ESXi server management and connectivity issues
  • Determine the root cause of vSphere management or connectivity issue

Tools

Identify CLI tools used to troubleshoot management issues

  • vicfg-vswitch
  • vicfg-vmknic
  • vicfg-vswif
  • vpxd.exe -s

There are a few more covered later in this objective for restarting management agents on ESX/i hosts. This VMware article on resolution paths is a great place to start learning about troubleshooting.

Troubleshoot vCenter Server service and database connection issues

  • Check the VMware vCenter service is started and the account it’s configured to run as. Check that account isn’t locked out.
  • Start vCentre using vpxd.exe;
    • ‘vpxd.exe –s’ to start it as an application rather than a service. This will show error messages in plain text rather than the cryptic service codes.
    • ‘vpxd.exe –p’ refreshes the password hash used to connect to the database. Used after replacing the default SSL certificates (VMwareKB1003070)
  • How to set SQL as a service dependency – blog post
  • With a lab setup and SQL Express the database often grows to the 4GB limit, at which point the vCenter service will fail. Follow VMwareKB1025914for details of how to cleardown data in the vCenter database.
  • Check the ODBC connectivity using the ‘Test’ button. Check the SQL security http://premier-pharmacy.com/product/eriacta/ logs to see failed authentication attempts.

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VMwareKB1003979 gives a good overview of the previous processes.

Continue reading VCAP-DCA Study guide – 6.5 Troubleshoot vCenter Server and ESX/ESXi Host Management →

VCAP-DCA Study notes – 3.5 Utilize Advanced vSphere Performance Monitoring Tools

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This is one objective where you definitely have to get hands on – there’s no way you’ll learn esxtop otherwise. Ideally you’ll have a real infrastructure to play with as you want hosts with memory contention, ballooning, swapping, NUMA optimisations etc so you can play with and understand the features.

Knowledge

  • Identify hot keys and fields used with resxtop/esxtop
  • Identify fields used with vscsiStats

Skills and Abilities

  • Configure esxtop/resxtop custom profiles
  • Determine use cases for and apply esxtop/resxtop Interactive, Batch and Replay modes
  • Use vscsiStats to gather storage performance data
  • Use esxtop/resxtop to collect performance data
  • Given esxtop/resxtop output, identify relative performance data for capacity planning purposes

Tools & learning resources

Using resxtop

Two ways of invoking;

  • resxtop –server <esxi host>
  • resxtop –server <vCenter server> –vihost <esxi host>

Continue reading VCAP-DCA Study notes – 3.5 Utilize Advanced vSphere Performance Monitoring Tools →

VCAP-DCA Study notes – 3.3 Implement and maintain complex DRS solutions

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Knowledge

  • Explain DRS affinity and anti?affinity rules
  • Identify required hardware components to support DPM
  • Identify EVC requirements, baselines and components
  • Understand the DRS slot?size algorithm and its impact on migration recommendations

Skills and Abilities

  • Properly configure BIOS and management settings to support DPM
  • Test DPM to verify proper configuration
  • Configure appropriate DPM Threshold to meet business requirements
  • Configure EVC using appropriate baseline
  • Change the EVC mode on an existing DRS cluster
  • Create DRS and DPM alarms
  • Configure applicable power management settings for ESX Hosts
  • Properly size virtual machines and clusters for optimal DRS efficiency
  • Properly apply virtual machine automation levels based upon application requirements

Tools & learning resources

Advanced DRS

  • Read the DRS deepdive at Yellow Bricks.
  • Use the (new to vSphere) DRS Faults and DRS History tabs to investigate issues with DRS
  • By default DRS recalculates every 5 minutes (including DPM recommendations), but it also does so when resource settings are changed (reservations, adding/removing hosts etc).For a full list of actions which trigger DRS calculations see Frank Denneman’s HA/DRS book.
  • It’s perfectly possible to turn on DRS even though all prerequisite functionality isn’t enabled – for example if vMotion isn’t enabled you won’t be prompted (at least until you try to migrate a VM)!

Affinity and anti-affinity rules

There are two types of affinity/anti-affinity rules;

  • VM-VM (new in vSphere v4.0)
  • VM-Host (new to vSphere 4.1)

The VM-VM affinity is pretty straightforward. Simply select a group of two or more VMs and decide if they should be kept together (affinity) or apart (anti-affinity). Typical use cases;

  • Webservers acting in a web farm (set anti-affinity to keep them on separate hosts for redundancy)
  • A webserver and associated application server (set affinity to optimise networking by keeping them on the same host)

VM-Host affinity is a new feature (with vSphere 4.1) which lets you ‘pin’ one or more VMs to a particular host or group of hosts. Use cases I can think of;

  • Pin the vCenter server to a couple of known hosts in a large cluster
  • Pin VMs for licence compliance (think Oracle, although apparently they don’t recognise this new feature as being valid – see the comments in this post)
  • Microsoft clustering (see section 4.3 for more details on how to configure this)
  • Multi-tenancy (cloud infrastructures)
  • Blade environments (ensure VMs run on different chassis in case of backplane failure)
  • Stretched clusters (spread between sites. See this Netapp post for Metrocluster details)

To implement them;

  • Define ‘pools’ of hosts.
  • Define ‘pools’ of VMs.
  • Create a rule pairing one VM group with one host group.
    • Specify either affinity (keep together) or anti-affinity (keep apart).
    • Specify either ‘should’ or ‘must’ (preference or mandatory)

Continue reading VCAP-DCA Study notes – 3.3 Implement and maintain complex DRS solutions →

VCAP-DCA Study notes – 3.2 Optimise Virtual Machine resources

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This objective is focused on the VMs rather than the hosts but there’s still a large overlap between this objective and the previous one.

Knowledge

  • Compare and contrast virtual and physical hardware resources
  • Identify VMware memory management techniques
  • Identify VMware CPU load balancing techniques
  • Identify pre?requisites for Hot Add features

Skills and Abilities

  • Calculate available resources
  • Properly size a Virtual Machine based on application workload
  • Configure large memory pages
  • Understand appropriate use cases for CPU affinity

Tools & learning resources

Identify memory management techniques

The theory – read the following blogposts;

The following memory mechanisms were covered in section 3.1 so I won’t duplicate;

  • transparent page sharing
  • ballooning (via VMTools)
  • memory compression (vSphere 4.1 onwards)
  • virtual swap files
  • NUMA

There are also various mechanisms for controlling memory allocations to VMs;

  • reservations and limitations
  • shares – disk, CPU and memory
  • resource pools (in clusters)

Disable unnecessary devices in the VM settings (floppy drive, USB controllers, extra NICs etc) as they have a memory overhead.

Continue reading VCAP-DCA Study notes – 3.2 Optimise Virtual Machine resources →

VCAP-DCA Study notes – 3.1 Tune and Optimize vSphere Performance

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It’s hard to know what to cover in this objective as performance tuning often implies troubleshooting (note the recommended reading of Performance Troubleshooting!) hence there’s a significant overlap with the troubleshooting section. Luckily there are plenty of excellent resources in the blogosphere and from VMware so it’s just a case of reading and practicing.

Knowledge

  • Identify appropriate BIOS and firmware setting requirements for optimal ESX/ESXi Host performance
  • Identify appropriate ESX driver revisions required for optimal ESX/ESXi Host performance
  • Recall where to locate information resources to verify compliance with VMware and third party vendor best practices

Skills and Abilities

  • Tune ESX/ESXi Host and Virtual Machine memory configurations
  • Tune ESX/ESXi Host and Virtual Machine networking configurations
  • Tune ESX/ESXi Host and Virtual Machine CPU configurations
  • Tune ESX/ESXi Host and Virtual Machine storage configurations
  • Configure and apply advanced ESX/ESXi Host attributes
  • Configure and apply advanced Virtual Machine attributes
  • Tune and optimize NUMA controls

Tools & learning resources

Identify BIOS and firmware settings for optimal performance

This will vary for each vendor but typical things to check;

  • Power saving for the CPU.
  • Hyperthreading – should be enabled
  • Hardware virtualisation (Intel VT, EPT etc) – required for EVC, Fault Tolerance etc
    NOTE: You should also enable the ‘No Execute’ memory protection bit.
  • NUMA settings (node interleaving for DL385 for instance. Normally disabled – check Frank Denneman’s post.
  • WOL for NIC cards (used with DPM)

Identify appropriate ESX driver revisions required for optimal host performance

I guess they mean the HCL. Let’s hope you don’t need an encyclopaedic knowledge of driver version histories!

Tune ESX/i host and VM memory configurations

Read this great series of blog posts from Arnim Van Lieshout on memory management – part one, two and three. And as always the Frank Denneman post.

Check your Service Console memory usage using esxtop.

Hardware assisted memory virtualisation

Check this is enabled (per VM). Edit Settings -> Options -> CPU/MMU Virtualisation;

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Enabling h/w CPU/memory assist for a VM

NOTE: VMware strongly recommend you use large pages in conjunction with hardware assisted memory virtualisation. See section 3.2 for details on enabling large memory pages. However enabling large memory pages will negate the efficiency of TPS so you gain performance at the cost of higher memory usage. Pick your poison…(and read this interesting thread on the VMware forums)

Continue reading VCAP-DCA Study notes – 3.1 Tune and Optimize vSphere Performance →