Archive for the ‘Virtualization Basics’ Category

Support for PST in Network Drives

July 26, 2011 1 comment

One of the main challenges on VDI has always been around use of Outlook PST’s.Although PST’s are meant to be used as archiving or backup solutions , Smaller mail box size in large Organizations meant that People use PST all the time. I would not like to get into a discussion if one should use PST or not. As a VDI administrator ,  I might be against the use of PST’s but then decision varies from Organization to Organization and we have to live with it. PST’s are generally stored on Home drives ( Data Drive) that are presented to a User in a VDI session. Predominantly , Home Drives are carved out of NAS or on a more generic term “Network Drives”.  Until now , PST’s accessed over Network was not a supported Microsoft Configuration  which meant that you cannot log a case with Microsoft for any issues pertaining to use of PST’s on Network Drives.

Starting with Outlook 2010 , Microsoft has termed that “Network access of PST and OST as a Supported configuration” under specific conditions namely,

  • A high bandwidth/low latency network connection is used.
  • There is single client access per file (one Outlook client per .pst).
  • Windows Server 2008 R2 Remote Desktop Session Host (RDSH) and Virtual Desktop Infrastructure (VDI) are used.
This is a welcome change from a VDI Administrator perspective. There are always advantages and disadvantages of using PST on VDI and you would be the best person to judge if it’s suitable to your environment. Sometimes you don’t have a choice !
More details on Support for PST in Network Drives can be found in this Microsoft KB and would recommend reading the Planning Consideration White paper that can be found here.

Microsoft Hyper-V vs. VMware ESX

April 10, 2011 8 comments

This is not just another post to compare VMware ESX with Microsoft Hyper-V since i certainly believe without any doubt at this moment VMware ESX is leaps ahead of other competing hypervisors including Microsoft Hyper-V. What Microsoft has done with Sp1 for Windows 2008 R2 is introduce couple of cool features in Dynamic Memory and Remote FX to Hyper-V but these are not game changers. In this post , I am just trying to portray the  advantages and short comings of both ESX and Hyper-V.

What works for VMware ESX ?

  • Virtual Center, the management console of VMware for managing multiple ESX Servers generally does not get the credit it deserves. A single management console for managing , monitoring and patching of ESX hosts and the Guest VMs and it’s Applications makes administrator’s work easier.
  • Ability to configure Customized roles for administrators in Virtual Center.
  • Huge list of supported of Guest Operating Systems
  • Memory Management features such as TPS , Ballooning , Swapping and Memory compression.
  • HA & DRS Clustering capability of ESX is technologically superior to Microsoft’s Hyper-V Cluster giving the ability to provide high availability to VMs and at the same time distributing loads evenly across the hosts.
  • Fault Tolerance capability of VMware ESX
  • Third party plugin support from various vendors like EMC , NetApp , f5 , Dell etc.. that helps administrators manage them from Virtual Center
  • Advanced technologies like Storage vMotion , Storage IO Control , Network IO Control , Host Profiles and DPM ( Distributed Power Management)
  • VAAI (vStorage API for Array Integration)  helps offload the load of Storage related task on to Storage Array’s
  • Whole community of bloggers and lots and lots of free tools for VMware environment
  • VMware KB – Knowledge base site of VMware that is constantly updated and contains step by step resolution for most of the issues on VMware environment.
  • Stability/Resiliency of ESX

What VMware ESX lacks ?

  • There is no single management console for managing multiple free ESXi Servers. This can be achieved for Hyper-V using Hyper-V Manager..
  • Cost – Costlier when compared to Hyper-V but one has to consider the amount of features that comes packed with ESX which makes ESX worth every penny spent !!

What works for Microsoft Hyper-V ?

  • Microsoft recommends Hyper-V as part of their solutions and tight integration and support with various other products of the Microsoft Eco-system helps in adoption of Hyper-V.
  • Hyper-V Manager that helps in managing multiple Hyper-V Servers from a single console . Please note that there is limited functionality but still one can manage multiple Hyper-V Servers from a single console.
  • Cost ( Hyper-V is part of Windows 2008 family of products) – If the Virtual machines that run on Hyper-V are based on Windows , the cost associated with Hyper-V goes down dramatically since in a VMware environment we have to account the OS cost of VM’s as well.

What Hyper-V lacks ?

  • Dependency on multiple applications for managing ( SCVMM) , monitoring ( SCOM) and patching (SCCM/WSUS) of Hyper-V hosts and VMs and also the fact that there is no tight integration between these components.
  • Lack of Customizable roles for Administrators in Hyper-V Manager and SCVMM
  • Resiliency/Stability of Hyper-V cannot match that of ESX
  • Lack of advanced technologies supported by ESX like Storage vMotion , SIOC , NIOC , VAAI etc…

These are my personal opinion of what works for the hypervisors and what they lack ? Would love to hear your comments as well.

Post P2V Tasks

January 9, 2011 1 comment

P2V does not end with migrating a Physical Server to Virtual Server  but there are certain post P2V tasks that could help in improving the performance of the converted server. 

  • Ensure you install VMware Tools on the migrated VM without fail.
  • Remove all unwanted hardware components from a migrated virtual server like serial ports and floppy drives.
  • Change the CPU and memory of the VM as per requirement and do not go with default values as they reflect the resources as in the Physical Server.
  • Physical Servers are installed with OEM drivers which are resource consuming and these drivers can be removed using Add/Remove Programs once they have been converted to VMs.

I came across a HP utility that can be download from here  which can be used to remove HP PSP with a single click.

One of the issue that is reported is the error when they get when try to assign IP to the migrated server –  ” The IP address XXX.XXX.XXX.XXX…” is already assigned to another adapter”.

This error message is caused by Ghosted NIC Cards that are present. These are the NIC cards that are converted as part of the P2V process since they were part of the physical Server but does not show up on the device manager. Follow the below mentioned steps to uninstall the ghost NIC cards.

  • Click Start –>Run–>Cmd [ Open a Command prompt]
  • Type in “set devmgr_show_nonpresent_devices=1” [ This change would display all non-present devices in device manager]
  • From the command prompt, type in “devmgmt.msc” [Do not go to Run prompt to open device manager or open from a GUI since above change would be effective from cmd prompt only]


  • Click View –>Show Hidden Devices
  • Non-Present devices are grayed out and can be uninstalled from the server. In this case  out NIC cards has to be uninstalled.


  • Now try assigning the IP back to the NIC card in the Virtual Server and should work fine.

IP Address issue has been addressed by Microsot here and VMware here and lot of other bloggers too.

Best Practices Analsyer for Hyper-V

July 24, 2010 1 comment

BPA or the Best Practices Analyser is a tool available for Microsof t Products like Exchange , SQL that would scan its configuration against the Best Practices prescribed by Microsoft for that product and give a report.  We can use the BPA for Hyper-V to scan a Windows 2008 R2 server that is running the Hyper-V role, and help identify configurations that do not comply with the best practices prescribed by Microsoft .


This is available as an update and can be downloaded and installed on Windows 2008 R2 Servers running Hyper-V Role .  BPA scans the configuration of the physical computer, the virtual machines, and other resources such as virtual networking and virtual storage . No configuration changes are made to the system .


How to run a BPA on a Hyper-V System ?


First ,  Download and Install the BPA Update for Microsoft Hyper-V from here . Please note that this is applicable for Windows 2008 R2 Systems with Hyper-V Role only.From a Windows 2008 Server , open Server manager and connect remotely to the  Hyper-V Server ( Assuming the Hyper-V Server is running on a Windows 2008 R2 Core ).Expand Roles and Click on Hyper-VOn the Right Pane , Select ” Scan this Role  ” that is available as part of the Best practice Analyser section as shown below




The BPA scans and presents list of Compliant . Non -Compliant and excluded report as shown above.

We can also double click on the Non-Compliant parameters and see the Issue , Impact and resolution that can be carried out to rectify the same .

For Example , the above picture indicates a warning for using Dynamic VHDs being used . Double-Click and the Issue , Impact and resolution would be presented as shown below :




Administrators can now use  BPA for Hyper-V to scan against Microsoft recommendations and then implement any changes that are necessary .


Categories: Hyper-V, Virtualization Basics Tags: ,

Hyper-threading on VMware vSphere

July 21, 2010 20 comments

Hyper-threading :

Hyper-threading is an Intel-proprietary technology used to improve parallelization of computations. For each processor core that is physically present, the Operating System  addresses two logical processors, and shares the workload between them when possible. With Hyper-threading a single processor core can execute two independent threads simultaneously . Performance improvements on hyper-threaded machines are dependent on the application and work loads . We might see slight performance improvements in certain applications while certain application performance might degrade as cache is shared between logical processors .

To enable or not to enable Hyper-threading on Hypervisor hosts has always been a debatable question with no clear winners .  HT cannot double the performance of a processor but it can certainly help in improving the performance slightly depending on the work load .

I have tried to consolidate and mention some considerations that would help administrators decide if to enable / disable  HT .

  • Hyper-threading has to be enabled in BIOS as well as in ESX . By default , HT is enabled in ESX
  • ESX can intelligently determine if a system  is enabled for hyper-threading and can load balance evenly across all cores of a processor.
  • Logical processors or threads on the same core will have consecutive numbers such as ,  for example CPU 0 and CPU 1 are on the first core of a processor . This has to be taken into account if CPU Affinity settings are used for Virtual machines
  • VMs are preferentially scheduled on two different cores rather than two logical processors on the same core .
  • In ESX , Administrators will be able to define HT core sharing options for individual VM’s in Advanced CPU option available in Resources tab while selecting individual Virtual machine’s Settings . Three options that are available would be :
  • Any – Default for all VM’s on a HT System . Virtual CPU of a VM can share cores with other Virtual CPU of the same VM as well Virtual CPU of other VM’s on the host.
  • None – Virtual CPU of a VM can never share core with other Virtual CPU of the same VM as well as Virtual CPU of other VM’s on the host.
  • Internal – Virtual CPU of a VM can share core only with other Virtual CPU of the same Virtual Machine.
  • Never bind two CPU intensive VMs to two logical processor of same core as it will be difficult to meet the resource demands of these intensive workloads

To conclude , From my personal experience , we have never enabled Hyper-threading in VI3 environments. With VI4 , We have enabled HT in certain environments and although we do not see much improvement in terms of performance we don’t see negative impact as well .  Enabling / Disabling Hyper-threading is a decision that is left to the administrators to decide after carefully analyzing their environments and work loads that constitutes them .

Would recommend all to have a look on the Hyper-threading in vSphere post by Performance Guru , Scott Drummonds , at on the CPU Scheduler improvements in ESX 4 and his recommendations.

Disk and Networking Concepts in Hyper-V

July 11, 2010 Leave a comment

Hyper-V is Microsoft’s Hypervisor which is shipped as part of Windows Server 2008 Family . In this blog series , I will share my views on Disk and Networking Concepts in Hyper-V .  Hyper-V Server can be managed using tools like Hyper-V manager and SCVMM just like VI Client that is used in vSphere to connect to Host / Virtual Center for management . Installation of Windows 2008 and enabling Hyper-V Role is straight forward and hence will not focus on them .

Introduction to Hyper-V :

Hyper-V is only available on the Standard, Enterprise and Data Center editions of Windows 2008 x64 and Windows 2008 R2 x64 . Windows Server 2008 / Windows Server 2008 R2 can be installed in either a full installation or Server Core installation. Hyper-V can be added as a role in either the full or server core installation. Please remember that full version of Windows Server 2008 cannot be downgrade to the Server Core version and vice versa also holds good. I personally prefer a Server Core Installation over a Full Installation as resource consumption , management overhead , attack surface and patching would be required less .

Virtual Storage Concepts ( VHDs) :

Virtual hard disks encapsulate a guest Virtual machine’s hard disk inside of a VHD file, which is placed on storage space  that is accessible to the host hyper-v server. Using VHDs provides benefits such as the ability to dynamically expand the disk, the ability to take snapshots of the disk, portability in terms of moving the disk to a different server, and so on.

There are three forms of virtual hard disks :

Dynamically Expanding Disks : Dynamically expanding virtual hard disks grows as data is added to the disk and hence consumes less space  . This can be compared to thin provisioning of storage .   The size of the .VHD file does not shrink automatically when data is deleted from the virtual hard disk. To reduce the size of the VHD file , We will have to compact the disk to by using the Edit Virtual Hard Disk Wizard. The dynamic expanding and manual shrinking of the disks may result on additional fragmentation of the host disk.

Fixed Size Disks : Fixed virtual hard disks provide storage capacity that is in the size specified when we create the virtual hard disk . The size of the .VHD file remains ‘fixed’ regardless of the amount of data we store on the VHD . We can use the Edit Virtual Hard Disk Wizard to increase the size of the virtual hard disk. Since we allocate full disk capacity at the time of creation itself , we will not have fragmentation issues at the host .
Differencing Disks : Differencing virtual hard disks provide storage to enable you to make changes to a parent virtual hard disk without altering that disk. The size of the .VHD file for a differencing disk grows as changes are stored to the disk. Different logical servers can share the same parent hard disk and have their own differencing disk for specific changes.

Pass-through : Attach a physical drive / LUN to a VM . Does not support Virtual Machine Snapshots . These are like RDMs that are used in VMware vSphere .

Networks :

We can use Virtual Network Manager to add, remove, and modify the virtual networks. Virtual Network Manager is available from Hyper-V Manager MMC. and also we can use SCVMM to add / remove / modify virtual switches. We can create many virtual networks on the server running Hyper-V to provide a variety of communications channels. Types are as mentioned below :

Private Network : Communications between virtual machines only.
Internal Network : Communications between the virtualization server and virtual machines.
External Network : Communications between a virtual machine and a physical network by creating an association to a physical network adapter on the host server.

It is always recommended to have a dedicated NIC for the Management interface that will be used by the Windows 2008 Root partition .

Integration Components on VMs installed on Hyper-V :

Integrations components (ICs) are sets of drivers and services that help your Virtual Machines have more consistent state and perform better by enabling the guest to use synthetic devices. This can be compared to VMware tools that is mandated in a VMware Environment . Some ICs that come with Hyper-V are VMBUS (transport for Synthetic devices), Time Sync (used to keep VM clocks in sync with the root partition sometimes called the host), Video Driver, Network Driver, Storage Driver. Windows Server 2008 will come with the integration components pre-installed and for all other Guest OS’s Integration components needs to be installed Manually .

Compatibility of Guest OS and Applications for Virtualization

July 6, 2010 Leave a comment
Is this Guest Operating System Supported on VMware ?
Is this Guest Operating System Supported on Hyper-V ?
Is this Application Supported on VM hosted on VMware vSphere ?
Is this Application Supported on VM hosted on Microsoft Hyper-V ?
In early days of an Organization’s Virtualization journey , These are the most common questions that is put across to Virtualization Administrators by the end users . Both VMware and Hyper-V have Supported Guest OS compatibility list which can be referred for the Suported Guest operating System list whereas the same is not the case with applications that are virtualized .  Administrators are made to check with the Application vendor for support  of their product on the various Virtualization platforms .  Microsoft Application’s supported configuration for both Hyper-V and VMware can be verified in the SVVP portal .
Please find list of links that can be helpful to VM Administrators in answering the above questions .
Supported Guest Operating System :
Microsoft Application supported Configuration :
We can use this link to verify if the configuration is supported by Microsoft by choosing the Application with the exact version  , Guest OS with SP and the Hypervisor in the Wizard .
Virtualizing Enterprise Applications in VMware :
VMware’s Compatibility Link can be used to verify VMware supported configuration for Systems , Storage/SAN, IO Devices, Guest/Host OS .
While other operating systems and Applications may still work with VMware / Hyper-V , this list shows the set of supported guest OS and Microsoft Supported Application configuration  on VMware / Hyper-V .
Please feel free to share your experiences and add more links that I might have missed so that I can update this blog accordingly .