Monthly Archives: April 2011

VCAP-DCA study notes completed!

This is a quick post to say that over the last few days I’ve been busily posting the last few objectives for the VCAP-DCA exam, and after quite a few months I’m finally http://premier-pharmacy.com/product-category/antibiotics/ done! You can download a PDF of the completed notes or refer to the VCAP-DCA index page for the online versions.

Enjoy!

VCAP-DCA Study notes 5.1 – Implement and Maintain Host Profiles

Host Profiles are a new feature to vSphere 4 but are only available to Enterprise+ licencees. As my company haven’t yet found a need for Enterprise+ features I’d not really worked with them before so this section was new to me. Interestingly the main reference given in the blueprint is the Datacenter Administration Guide which has very little about host profiles. The ESX/ESXi configuration guides have a small section on host profiles but not much, so the best reference is probably the VMware Host Profiles – Technical Overview whitepaper.

Skills and Abilities

  • Use Profile Editor to edit and/or disable policies
  • Create sub?profiles
  • Use Host Profiles to deploy vDS

Tools & learning resources

Host Profiles (VCP revision)

Basically host profiles are the equivalent of Microsoft’s Group Policy, but for VMware hosts.

  • Two primary uses
    • Ease deployment challenges (faster, more consistent)
    • Ongoing configuration control and audit reporting
  • Policy options (determining how a configuration setting is applied)
    • Use a fixed configuration
    • Ask the user how to configure it
    • Use an intelligent policy (using one or multiple criterion)
    • Disregard a setting
  • Works in a similar fashion to Update Manager;
  1. Create a baseline from a reference host.
  2. Attach the host profile to the hosts or clusters you want to configure
  3. Remediate (configure) the hosts or clusters
  4. Review compliance status
  • Unlike VUM it can’t remediate all the hosts in a cluster automatically (it won’t put them into maintenance mode for you etc). You can attach a profile to the cluster but you have to apply to each host manually (this is largely because the host profile may require user input).
  • Can only be used on vSphere hosts (not VI 3.x)
  • Must be created using a reference host, or imported from a previously created host profile.
  • Can be exported (in VMware Profile Format, *.vcf, which is XML content).  Host Profiles are not shared using vCentre Linked Mode, you have to export/import to other vCentre instances.
    NOTE: Administrator passwords aren’t exported as a security measure.
  • An ESX reference host can be applied to either ESX or ESXi. An ESXi reference host can ONLY be applied to another ESXi host.
  • When updating a host using a host profile you have to manually put the host in maintenance mode first. This is a significant issue for some people (although if you’re licenced for host profiles you’ve also got licences for vMotion and DRS so moving VMs off the host is potentially easier). Note that you need to enter maintenance mode even for trivial settings such as setting the time, timezone etc. Any setting which normally requires a reboot (changing service console memory for example) will still need a reboot.
  • You must have both host profile privileges (create, delete, edit etc) AND privileges to configure the area in question (Networking, Storage etc) for the operation to be allowed.

REAL WORLD: When building a new ESX/ESXi host it will have a 60 day eval period with all features enabled so even if you don’t have Enterprise+ licencing you can use host profiles for initial configuration.

Continue reading VCAP-DCA Study notes 5.1 – Implement and Maintain Host Profiles

VCAP-DCA Study notes – 3.4 Perform Capacity Planning in a vSphere environment

Knowledge

  • Understand the DRS slot?size algorithm and its impact on migration recommendations
  • Identify tools needed for monitoring capacity planning
  • Identify performance metrics related to resource contention and saturation

Skills and Abilities

  • Predict when additional ESX/ESXi Host, network or storage http://premier-pharmacy.com/product/nexium/ resources will be required by observing an existing environment
  • Determine when to expand or contract provisioned Virtual Machine resources based upon observed Virtual Machine utilization
  • Interpret performance metrics from vCenter to properly size the environment

Tools

Again there is a considerable overlap between this objective and the others in section three – the goal of understanding the DRS slot-size is an exact duplicate from section 3.3!

DRS slot size algorithm and its impact on migration recommendations

This was covered in section 3.3. You can always reread the DRS deepdive at Yellow Bricks.

Identify tools needed for monitoring capacity planning

  • vCenter Performance Charts
  • vCenter Storage views
  • esxtop (particularly in batch or reply mode)
  • Perfmon
  • Third party tools (not likely in VCAP-DCA exam though)

Consider SCSI reservations per LUN, number of VMs per LUN. Adaptive vs predictive LUN sizing.

Predict when additional ESX/ESXi Host, network or storage resources will be required by observing an existing environment

Refer to section 3.1 for the metrics to check. Ballpark;

  • Memory – how much is in the host compared to active memory used? Factor in reservations etc
  • Network – any dropped packets? Might imply greater bandwidth required…
  • CPU – check for long term patterns using Performance Charts.
  • I/O – high latency or lack of capacity are the main indicators to look for

Interpret performance metrics from vCenter to properly size environment

Be aware what the various metrics actually show you. For example what’s the difference between Host Memory and Guest Memory in the screenshot below?? The answers can be found in VMworld session TA8129 Beginners guide to performance management.

vCenter statistics

vCenter and ESXTOP present statistics differently. While ESXTOP tends to display a more useful figure (%CPU ready for example) the value presented in vCenter needs to be calculated depending on the time interval.

Remember that vCenter summary statistics can sometimes mislead – memory per host looks fine in the screenshot above but you might find NUMA locality is low (for example).

VCAP-DCA Study guide – 6.4 Troubleshooting Storage Performance and Connectivity

Knowledge

  • Recall vicfg-* commands related to listing storage configuration
  • Recall vSphere 4 storage maximums
  • Identify logs used to troubleshoot storage issues
  • Describe the VMFS file system

Skills and Abilities

  • Use vicfg-* and esxcli to troubleshoot multipathing and PSA?related issues
  • Use vicfg-module to troubleshoot VMkernel storage module configurations
  • Use vicfg-* and esxcli to troubleshoot iSCSI related issues
  • Troubleshoot NFS mounting and permission issues
  • Use esxtop/resxtop and vscsiStats to identify storage performance issues
  • Configure and troubleshoot VMFS datastores using vmkfstools
  • Troubleshoot snapshot and resignaturing issues

Tools

There’s obviously a large overlap between diagnosing performance issues and tuning storage performance, so check section 3.1 in tandem with this objective.

Recall vicfg-* commands related to listing storage configuration

  • vicfg-scsidevs
  • vmkiscsi-tool
  • vicfg-mpath
  • vicfg-iscsi
  • esxcli corestorage | nmp | swiscsi
  • vicfg-nas
  • showmount -e
  • esxtop/resxtop
    • look for CONS/s – this indicates SCSI reservation conflicts and might indicate too many VMs in a LUN. This field isn’t displayed by default (press ‘f’ then ‘f’ again to add it)
  • vscsiStats
  • vmkfstools
  • vicfg-module

Continue reading VCAP-DCA Study guide – 6.4 Troubleshooting Storage Performance and Connectivity

VCAP-DCA Study notes 6.2 – Troubleshoot CPU and Memory Performance

Knowledge

  • Identify resxtop/esxtop metrics related to memory and CPU
  • Identify vCenter Server Performance Chart metrics related to memory and CPU

Skills and Abilities

  • Troubleshoot ESX/ESXi Host and Virtual Machine CPU performance issues using appropriate metrics
  • Troubleshoot ESX/ESXi Host and Virtual Machine memory performance issues using appropriate metrics
  • Use Hot?Add functionality to resolve identified Virtual Machine CPU and memory performance issues

Tools & learning resources

This is another objective that’s hard to quantify – experience will be the main requirement! There are some great general purpose resources out there;

Note that resxtop (built in to the vMA) does not offer the ‘replay’ mode available in ESX classic. Source: VMworld session MA6580, vMA Tips and Tricks. Continue reading VCAP-DCA Study notes 6.2 – Troubleshoot CPU and Memory Performance