Home > Blogs > VMware Consulting Blog > Tag Archives: Travis Wood

Tag Archives: Travis Wood

The Anatomy of an Instant Clone

By Travis Wood

If you’ve used Horizon View over the last few years, then you most likely have come across linked clones. Linked clones use a parent image, called a “replica,” that serves read requests to multiple virtual machines (VMs), and the writes in each desktop are captured on their own delta disk. Replicas can also be used to change desktop update methodologies; instead of updating every desktop, you can update the parent image and recompose the rest of the desktops.

Horizon 7 has introduced a new method of provisioning with Instant Clones. Instant Clones are similar to linked clones in that all desktops read from a replica disk and write to their own disk, but Instant Clone takes it one step further by doing the same thing with memory. Instant Clones utilize a new feature of vSphere 6 where desktop VMs are forked (that is, Instant Clones are created) off a running VM—instead of cloning a powered-off VM—which provides savings for provisioning, updates, and memory utilization.

Golden Image

With Instant Clones you start with your golden image, in a way that is similar to linked clones. The golden image is the VM you install the operating system on, then join to the domain, and install user applications on; you follow the same OS optimizations procedures you would use for Instant Clones.

When you’re done, release its IP address, shut it down, and create a snapshot. Now you are ready to create your Instant Clone desktop pool. This VM should have VM Tools installed, along with the Horizon Agent with the Instant Clone module. It is NOT possible to have the Instant Clone and Composer modules co-installed, so you will always need different snapshots if using Instant Clones and linked clones from the same golden image. Reservations can be set on the golden image and they will be copied to the Instant Clones, reducing the size of the VSwap file. It is important to note that the golden image must be on storage that’s accessible to the host you are creating your Instant Clone desktop pool on.

Template

When you create your pool, Horizon will create a template. A template is a linked clone from your golden image, created on the same datastore as the golden image. It will have the name cp-template, and will be in the folder ClonePrepInternalTemplateFolder. Template disk usage is quite small, about 60 MB. There will be an initial power-on after the template is created, but it will then shut off.

TWood_Horizon Template

Replica

Next, Horizon will create a replica, which is the same as a Linked Clone replica. It is a thin-provisioned, full clone of the template VM. This will serve as the common read disk for all of your Instant Clones, so it can be tiered onto appropriate storage through the Horizon Administrator console, the same way it is done with Linked Clones. Of course, if you are using VSAN, there is only one datastore, so tiering is done automatically. Horizon will also create a CBRC Digest file for the replica. The replica will be call cp-replica-GUID and will be in the folder ClonePrepReplicaVmFolder. The disk usage of the replica will be depend on how big your Gold Master is, but remember, it’s thin provisioned and not powered on, so you will not have VSwap functionality.

TWood_Horizon Replica

Parent

Horizon will now create the final copy of the original VM, called a parent, which will be used to fork the running VMs. The parent is created on every host in the cluster; remember, we are forking running VMs here, so every host needs to have a running VM. These will be placed on the same datastore as the desktop VMs, where there will be one per host per datastore. Because these are powered on, they have a VSwap file the size of the allocated vMEM. In addition, there will be a small delta disk to capture the writes booting the parent VM and the VMX Overhead VSwap file, but this—and the sum of the other disks—is relatively small, at about 500 MB. These will be placed in ClonePrepReplicaVmFolder.

TWood_Horizon Parent

Something you’ll notice with the parent VM is that it will use 100% of its allocated memory, causing a vCenter alarm.

TWood_vCenter Alarm

TWood_Virtual Machine Error

Instant Clones

OK! At this point, we are finally ready to fork! Horizon will create the Instant Clones based on the provisioning settings, which can be upfront or on-demand. Instant Clones will have a VSwap file equal to the size of the vMEM—minus any reservations set on the Gold Master, plus a differencing disk.

The amount of growth for the differencing disk will depend on how much is written to the local VM during the user’s session, but it is deleted on logout. When running View Planner tests, this can grow to about 500 MB, which is the same as when using View Planner for Linked Clones. The provisioning of Instant Clones will be fast! You’ll see much lower resource utilization of your vCenter Server and less IO on your disk subsystem because there is no boot storm from the VMs powering on.

TWood_vCenter Server

Conclusion

Instant Clones are a great new feature in Horizon 7 that take the concept of Linked Clones one step further. They bring the advantages of:

  • Reducing boot storms
  • Decreasing provisioning times
  • Decreasing change windows
  • Bringing savings to storage utilization

Instant Clones introduce a number of new objects: replicas, parents, and templates. It is important to understand not only how these are structured, but also their interrelationships, in order to plan your environment accordingly.


Travis is a Principal Architect in the Global Technology & Professional Services team, specializing in End User Computing.  He is also a member of the CTO Ambassadors program which connects the global field with R&D and engineering.

Common VCDX-DTM Questions Answered by a Double VCDX

Travis Wood

 

By Travis Wood

Last year the VCDX-DTM track was released and Simon Long, Ray Heffer and myself became the first to be certified in this new certification. Since then I have sat on several panels and fielded a lot of questions specific to the desktop certification track, so I wanted to answer some of those frequently asked questions here on how to prepare for this track.

I have a View design, should I submit for VCDX-DCV or VCDX-DTM?

If your design is focused on View and EUC then you will likely be better prepared if you submit for a VCDX-DTM. Whilst you can, and people have in the past, use a View design for DCV, you still need to demonstrate mastery of skills applicable to DCV designs. The criteria for VCDX-DTM is specifically designed to evaluate desktop designs, so this is likely the better option for a View design, and if this is where your core skills are then this will give you better preparation for your defence.

What products are in-scope for VCDX-DTM?

As specified in the VCDX-DTM Blueprint, VCDX-DTM is focused on the VMware Horizon suite to deliver end-user computing solutions. Within this product suite there are a number of products that may be utilized to meet your requirements including Horizon View, Mirage, Identify Manager and vCenter Operations for Horizon. Also vSphere makes up a key component of a desktop virtualization design.

Does the design have to be based on Horizon View?

Whilst the blueprint does not specifically say that Horizon View must be used, it would be extremely difficult if not impossible to cover the required solution areas without it.

Do I need to use ThinApp or AppVolumes?

Application integration is important to a VDI design but may be achieved in different ways depending on your requirements and constraints. These specific products are not required, but you might want to consider how you will demonstrate the application integration that is in your design, and be prepared for questions that may arise in the design or troubleshooting scenarios.

Do I have to use a VMware product for profile management?

Not necessarily – there are many ways to handle profile management and the best solution for your design should be used. But if you do include third-party profile management, do not simply mention it – ensure ALL documentation includes the detail required to design and implement the solution correctly.

Do I need to know about products other than Horizon View?

Even if your design does not use products such as Mirage or AppVolumes, prepare yourself for being presented with business requirements that could be solved using these products – or in other ways. Having a breadth of knowledge of the VMware EUC portfolio will give you greater capability to solve problems presented by the design and troubleshooting scenarios.

Is AirWatch in-scope of VCDX-DTM?

VCDX-DTM is focused on the Horizon Suite, and AirWatch is not a part of Horizon Suite.

Is my design large or complex enough?

There are no specific size or complexity requirements, but the design must be “enterprise-scale.” This is the same requirement that was specified by both DCV and DT; neither size nor complexity at either end of the scale will guarantee success. The panellists are looking for the candidate to demonstrate mastery of the solution areas defined in the blueprint. Choose a design that allows you to do this.

Can I modify my design?

Absolutely! The most valuable advice I got when preparing for my first VCDX is that you can modify your actual design to better demonstrate mastery. This may be adding or removing elements to achieve a better design that will demonstrate your ability to design a solution across all of the solution areas.

Hopefully these answers will help clear up some questions. If you have any further questions please tweet me at @vTravWood.


Travis Wood is a VMware Senior Solutions Architect

Understanding View Disposable Disks

Travis WoodBy Travis Wood, VCDX-97

When VMware introduced Linked-Clones in View 4.5 there was a new type of disk included called the Disposable Disk. The purpose of this disk was to redirect certain volatile files away from the OS Disk to help reduce linked-clone growth.  I have read a lot of designs that utilize disposable disks but it has become clear that there is a lot of confusion and misunderstanding about what they do and exactly how they function.  This confusion is highlighted in a View whitepaper called View Storage Considerations which describes disposable disks as:

Utilizing the disposable disk allows you to redirect transient paging and temporary file operations to a VMDK hosted on an alternate datastore. When the virtual machine is powered off, these disposable disks are deleted.

The three elements from this paragraph I want to demystify are:

  1. What is redirected to the disposable disk?
  2. Where are disposable disks hosted?
  3. When are disposable disks deleted/refreshed?

What is redirected?

By default there are three elements that are redirected to the disposable disk.  The first is the Windows swap file, View Composer will redirect the Swap file from C: to the disposable disk. It is recommended to set this to a specific size to make capacity planning easier.

 

TWood1

 

The other elements that are redirected are the System Environment Variables TMP and TEMP.  By default, the User TEMP and TMP Environment Variables are NOT redirected.  However it is highly recommended to remove the User TEMP and TMP Environment variables, if this is done then Windows will use the System Variables instead and the user temporary files will then be redirected to the disposable disk.

TWood4

 

 

Where is the disposable disk stored?

There is a common misconception that like the User Data Disk, the Disposable Disk can be redirected to a different tier.  This is not the case and the Disposable Disk is always stored with the OS Disk.  In later versions of View you can choose the drive letter within the GUI for the Disposable Disk to avoid conflicts with mapped drives, but this setting and the size are the only customizations you can make to the disposable disk.

When is the disposable disk refreshed?

This is the question that tends to cause the most confusion.  Many people I have spoken to have said that it is refreshed when the user logs off, whilst others say it’s on reboot.  The Disposable Disk is actually only refreshed when View powers off the VM. User initiated shutdown & reboots as well as power actions within vCenter do not impact the disposable disk.  The following actions will cause the disposable disk to be refreshed:

  • Rebalance
  • Refresh
  • Recompose
  • VM powered off due to the Pool Power Policy set to “Always Powered Off”

This is quite important to understand, as if the Pool Power Policy is set to any of the other settings (Powered On, Do Nothing or Suspend) then your disposable disks are not getting refreshed automatically.

What does all this mean?

Understanding Disposable Disks and their functionality will enable you to design your environment appropriately.  The View Storage Reclamation Feature that was introduced in View 5.2 uses an SE Sparse disk for the OS Disk, this allows View to shrink OS disks if files are deleted from within the OS.  However only the OS disk is created as an SE Sparse disk, User Data Disks and Disposable Disks are created as a standard VMDK.  The key difference with this feature compared with Disposable Disks, is it relies on files being deleted from within the Guest Operating System, where as the Disposable Disk is deleted along with all the files it contains when View powers off the VM.  It is also important to note, that currently SE Sparse disks are not supported on VSAN.

If you choose to use Disposable Disks in your design, then depending on your power cycle you may want to add an operational task for administrators to periodically change the Power On setting for the pool within a maintenance window to refresh the Disposable Disk.  This is particularly important for the use case of Persistent Desktops which have long refresh/recompose cycles.


Travis Wood is a VMware Senior Solutions Architect