Friday, February 22, 2013

PernixData - An overview and a lot of excitement!

I could not stop myself to write this article as I was pretty excited about what I am hearing and reading about PernixData. 

PernixData is a start-up which is trying to innovate the old and left alone technology of Server Side Caching which could be a paradigm shift in the the field of how Datacenter and Virtualization works today.

They have come up with a Flash Virtualization Solution for Server side cache, which can sit on the ESXi host and can directly talk to vmkernel to cache IO on the ESXi on a Flash Drive. The cool part is that the PernixData FVP (Flash Virtualization Platform) actually is a distributed caching mechanism for a cluster of ESXi servers which can be a phenomenal product if it works the way the company claims.

This means that the customers DO NOT have to buy newer better arrays or disks, if the existing arrays do not support the throughput and I/O requirements of virtual machine workloads. Since the high speed caching layer will hold the data and will ensure performance while giving high availability it is a win-in situation for a customer. This can be revolutionary as this would reduce the need of upgrading storage arrays due to performance problems and save a ton of money for organizations.

"PernixData Flash Virtualization Platform (FVP) - an enterprise-class, high-speed, software-only data tier for application acceleration - enables a strategic shift in customers’ vision for virtualized data centers. PernixData FVP is created by virtualizing server-side flash via a scale out architecture. Virtualized applications transparently leverage FVP for unprecedented performance while requiring no changes to either the application or the underlying storage infrastructure. Clustered hypervisor features such as live migrations and distributed resource management continue to operate seamlessly with FVP. By virtualizing flash in servers, PernixData is picking up where hypervisors left off after virtualizing CPU and memory."

Source -

You know the brains behind this?? Its an ex-VMware employee named Satyam Vaghani, he was one of the engineer who developed VMFS (needless to say anything else about the credentials)

To read more about it:-

If things work, it might be another possible acquisition option for VMware to complete their Software Define Storage Strategy. Cannot wait to put my hands on it.. :-)

Wednesday, February 20, 2013

VMware Virtualization Blogs - Vote for the best in business!

Just wanted to notify all the readers about the voting for the Top 10 Virtualization blogs in the industry which is opened now.

This is an yearly election which is conducted by by opening a poll to the VMware community to rate the best blogs around the globe. Lets look at what vSphere Land has to to say about this Survey.

"There are over 200 blogs dedicated to VMware and virtualization, here’s your chance to pick your favorites and determine the top blogs. The last voting was a year ago and new bloggers are springing up every month. "

I am happy to announce that vXpress is also a candidate for this voting this year. :-) It is absolutely a pleasure to be listed by side of the some Masters of vBlogging.

Here is whom I voted for :-

@Yellow Bricks (Duncan Epping)
@Long White Clouds (Michael Webster)
@Frank Denneman(
@Virtu-Al (Alan Renouf)
@The Saffa Geek (Gregg Robertson)

Would appreciate and encourage you to Vote for the top 10 blogs as this helps the Virtualization bloggers across the globe to compete hard and provide quality content.

So what are you waiting for, head on over and take the survey to cast your ballot and reward the best bloggers for their hard work and dedication by letting them know that you appreciate them.

Monday, February 11, 2013

Using the VMware Hardware Compatibility List (HCL)!!

With each project kick-off or a knowledge transfer session, I emphasize on the importance of VMware Hardware Compatibility List as being the bible for making procurement and implementation decisions for any  piece of hardware for your VMware environment.

The Hardware Compatibility List, more popularly known as VMware HCL within VMware, is a single point of reference for you to ensure that any hardware which you are planning to use with your VMware software has been tested and certified to work fine. I have seen the HCL evolved tremendously over the past few years and now it has become a robust and a reliable tool to provide information which you would need before taking your procurement decisions.

The HCL is a very famous and popular tool amongst those who are a part of VMware community, but I thought it would be a good idea to blog about it and make this easy reference document which tells you how to use this tool effectively and quickly to find out any information which you need about hardware compatibility. The other reason is to ensure the the NEWBIES in the VMware community learn about this strong yet simple tool to make their life easier.

All right, let's begin with how to get to the VMware Hardware Compatibility List:-

Accessing VMware Hardware Compatibility List

2- Hover your mouse pointer on Support & Downloads & Click on Compatibility Guides

3- On the new page which appears click on View the VMware certified Compatibility Guides.

Once you are the Hardware Compatibility Search screen, you have 2 options from hereon, either you can use the Standard Search of click on a hyperlink which takes you to the Guided Search. See the screenshot below:-

Let us look at the Standard Search and then will have a quick look at the Guided Search.

Standard Search

The most important drop-down here is to select the type of Harware for which you are seeking compatibility. Click on the drop down next to the "What are you looking for" to see all the available options:-

I will take some time to explain the important one's:-

1-  Systems / Servers - As the name suggests, helps you find the compatible servers with all the releases of ESXi hypervisor. These servers can be Rack Mounter, Blade, Tower or from any Vendor such as HP, Dell, Cisco, IBM etc. There are multiple options under this search type for you to narrow down your search to your choice of server hardware. You can further drill down to stuff like the desirable BIOS version on a server to run a particular version of ESXi and much more.

2- Storage/SAN - Another important search criteria which helps you select the storage model and make and find compatibility for the same against a ESXi platform of your choice. This not only allows to check simple things such as make and model, but also allows you to drill down deeper and find out about VAAI (vStorage API for Array Integration) primitives support, Path policies recommended by the storage vendor, firmware or microcode level on the Storage Processors/Controllers & more.

3- VMware View - This option explore all the hardware possibilities for End user computing product line of VMware. From thin clients to supported protocols, all can be found here in this search.

4- Guest OS / Host OS - All the versions of Guest OS and Host OS supported on VMware Products at all the layers, whether end user or enterprise.

5- Site Recovery Manager - Searching for SRM compatibility with different types of SRA available from various storage vendors is something which can be easily found here, before implementing SRM in your infrastructure.

Along with these, there are others which are important and can be used to determine whether you have the right hardware to use VMware Products and features.

Now let's look at the Guided Search option.

Guided Search

For guided search you just need to click on link shown in the screenshots above. This will launch a simple wizard with a few easy to follow steps. Here is how it looks like:-

You have to go through the options and select what you are looking for. Ultimately you will get the results about the compatibility of VMware Products on the hardware which you have or want to procure.

I would strongly recommend you get familiar with this simple tool and use it without fail to ensure that you do not end up into situations which are unsupported by VMware Support.

I will leave you with other important links which you can use to take Compatibility and Interoperability decisions for your VMware environment and ensure that you always are in compliance by using the compatible and tested hardware. Following such practices would not only provide efficiency to your environment, but also provide up-time which is important to any business today

Partner Verified & Supported Products (PVSP) -

Applications Supported in VMware vSphere

To read more about applications supported on VMware vSphere refer to my previous blog article - 

Also, to see learn about more Tips on searching the VMware HCL refer to the following link - 

Hope this helps you take the correct decisions for your VMware Infrastructure.

Share this article to help others!!

Friday, February 1, 2013

ESXi/ESX host becomes Inaccessible/Not-Responding in vCenter after Un-Presenting Storage Luns

Today, I was responding to an e-mail from a system engineer from the VMware Partner Community. This was about an issue which they recently faced in a customer's VMware Infrastructure. This is reference with handling of Storage LUNS and Datastores on vSphere 4.x and 5.x platforms.

Here is the issue:-

"We have some unused data stores so we un-mounted those from all ESXi hosts and deleted the LUNs from storage. After that, the deleted datastores goes in a dead path state. One of the hosts in a cluster automatically disconnected from the vCenter. We re-scan HBA and  management services; however the dead paths still appear in the vCenter. We are not able to do vMotion and our HA master agent is also not working. How do we fix this??"

I have been asked similar questions time and again from customers, partners and fellow co-workers, hence I thought I should share this information with the larger community with this blog post.

How do you land up in this situation:-

Once you create a VMFS Datastore on a storage LUN, the state of this Datastore and the associated LUN is saved in the storage configuration of the ESXi Kernel. From here on, it is the responsibility of the vmkernel to ensure that the VMFS Datastore and the associated LUN is always available to the ESXi Hosts.

To ensure availability, the vmkernel sends I/O requests (SCSI Commands) to each of the Datastore after every few seconds and receives a response which ensures that the Datastores are up and running. This mechanism is to ensure that any transient storage conditions can be resolved and the LUNS/Datastores are available to the virtual machines.

Now coming to the situation mentioned above, where you have un-mounted, un-presented and destroyed the LUNS. In this situation, ESXi is not aware of the fact that whether you have un-presented these LUNS yourself or ESXi has lost them due to a technical failure. Now, with the default safety feature where-in ESXi will try to recover these LUNS, it will start sending requests to bring the state of the missing LUNS as ONLINE. Unfortunately, these LUNS are not available anymore; hence the requests of the ESXi hosts would not be honored. 

Since these request would go into a stale state, they would cause the Hostd service to hang. Hostd keeps a track of all the agent based services and resources available to ESXi. As soon as the Hostd service is in trouble,  the VPXA agent, HA Agents and the Hostd service itself will start falling apart, causing the host to disconnect from the vCenter Server. No vCenter means no vMotion etc.

Form above description, you can see the cascading effect of un-presenting LUNS from the ESXi servers without following a proper procedure which is available in a VMware KB article. Please note that this issue can happen in a day, weeks or even a month’s time of un-presenting the storage Luns.

How to solve this

Unfortunately, you are in a scenario where you have already hit the situation wherein the hostd service is crashing. You would have to perform a reboot of all the the ESXi servers which are showing the APD (All Paths Down) or PDL (Permanent Device Lost) warning messages in the vmkernel / Messages logs.

To read more on this you can refer to the following KB Article - Permanent Device Loss (PDL) and All-Paths-Down (APD) in vSphere 5.0

How to avoid this in the future

To avoid getting into such a situation in the future, please follow the proper procedure mention in the KB article – Un-mounting a LUN or Detaching a Datastore/Storage Device from multiple ESXi 5.x hosts

Hope this helps you to understand the basic concepts of how Storage LUNs need to be treated on an ESXi Server to ensure that storage operations do not affect the way how your VMware Infrastructure performs.