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How to automate vFRC configurations using the command-line in ESXi

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While working on my vSphere Flash Read Cache (vFRC) articles last week, I wanted to be able to quickly build out my vSphere environment so that vFRC was fully configured as part of my ESXi installation using a Kickstart script. This would allow me to simply add my ESXi hosts into vCenter Server and not have to go through the vSphere Web Client for each host configuring vFRC. Now of course the vSphere Web Client is not the only option to configure vFRC, you can also use the vSphere APIs by creating your own script or even using the new vFRC PowerCLI cmdlets as an alternative.

However, I was interested in creating a very simple script that I could easily integrate with my kickstart deployment as that is what I am using for automated provisioning of my Nested ESXi hosts. With a bit of research and some trial/error, I have come up with a process that can be fully automated from the command-line of ESXi. In my environment I have a Nested ESXi host that contains three SSD's (4GB each) which will be used to construct my Virtual Flash Resource.

Note: Jump to the very bottom for a completely automated script to configure vFRC for your ESXi host.

Step 1 -You will want to list out the available SSD devices on your ESXi host, you can do so by using the following ESXCLI command:

esxcli storage vflash device list

You will need to make a note of the device ID's as they will be required in the sub-sequent steps.

Step 2 - Next we will need to partition our devices before we can create VFFS (Virtual Flash File System) and we will need to calculate the end sector if we wish to consume the entire device. To do so, we will need to use the partedUtil command and specify the "getptbl" option to identify some information.

partedUtil getptbl /vmfs/devices/disks/naa.6000c2932c4ed8a540b6e9f0be9e1009

You will need to make a note of the first three numbers which represents number of cylinders, number of heads and number of sectors per track. To calculate the end sectors, the equation will be the following: (Number of Cylinders x Number of Heads x Number of Sectors Per Track) - 1

In our example we have (522*255*63)-1 which gives us 8385929

To create the partition, we will again use the partedUtil and specify "setptbl" option by running the following command (ensure to replace your end sector value):

partedUtil setptbl /vmfs/devices/disks/naa.6000c2932c4ed8a540b6e9f0be9e1009 "gpt" "1 2048 8385929 AA31E02A400F11DB9590000C2911D1B8 0"

For more details on using the partedUtil command, please refer here and here.

Since my other two devices are exactly the same size, I can just re-use the command and replace the device path. Ensure all devices that you wish to use in your Virtual Flash Resource is partition before moving onto the next step.

Step 3 - We will now create our VFFS volume which only needs to be created on one of the devices. In this example, I have chosen to use the first SSD device as shown in "esxcli storage vflash device list". To create the VFFS volume we will use the vmkfstools tool just like we would if we were creating a VMF volume but instead use the "vmfsl" type.

Run the following command to create your VFFS volume, you will need to append :1 to the end of the SSD device to specify the partition you created earlier as well as a display name of the volume which I chose vffs-$(hostname -s) which will use the short hostname of the ESXi host

vmkfstools -C vmfsl /vmfs/devices/disks/naa.6000c2932c4ed8a540b6e9f0be9e1009:1 -S vffs-$(hostname -s)

Step 4 - Once you have your VFFS volume created, you can extend it with additional SSD devices by using vmkfstools and specifying the -Z option. The syntax for the command is the SSD device partition you wish to add followed by the source SSD device containing the VFFS volume.

Here is an example of the command:

vmkfstools -Z /vmfs/devices/disks/naa.6000c29498be5c56231d631d9c6cbee8:1 /vmfs/devices/disks/naa.6000c2932c4ed8a540b6e9f0be9e1009:1

You will be prompted on whether you want to extend and to confirm enter value of 0.

You will need to do this for all SSD devices you partition earlier to be part of the same VFFS volume.

Step 5 - To confirm that everything was configured correctly, we will use vmkfstools to query our VFFS volume by running the following command and specifying the path to our VFFS volume:

vmkfstools -Ph /vmfs/volumes/vffs-vesxi55-10

From the output we should see the filesystem for the volume is of type VFFS and we should also see the three SSD devices that is backing this VFFS volume as shown in screenshot above.

Step 6 - Finally to make this new VFFS volume visible to the ESXi host, we will need to refresh the ESXi storage system and we can do so by running the following vim-cmd:

vim-cmd hostsvc/storage/refresh

At this point, we now have a fully configured VFFS volume. If you jump right into the vSphere Web Client expecting to see your new Virtual Flash Resource on your newly configured ESXi host, you might be in for a surprise! You will actually NOT see the VFFS volume that we just configured which stumped me initially.

It turns out simply creating a VFFS volume does not automatically equate to configuring a Virtual Flash Resource. You still need to configure the ESXi host to add the Virtual Flash Resource based on your VFFS volume and in my opinion that seems to be quite odd and counter-intuitive. Today there is no CLI command to add the Virtual Flash Resource, you would need to use either the vSphere Web Client or use the vFRC vSphere API. If you login to the vSphere Web Client and configure a Virtual Flash Resource, you will see the VFFS volume that we have created and you just need to select it and it will automatically add it.

This is not very ideal if you want to completely automate vFRC configurations and I decided to leverage my knowledge of the vFRC vSphere APIs and create a very simple python script that would call into the ESXi host's MOB and issue the HostConfigureVFlashResource() method. This was sort of a quick/dirty way to call the vSphere API and add in the Virtual Flash Resource.

Disclaimer: These scripts are provided as examples, please test these scripts in your development/test environment before running them in production.

To make this really useful I have created two scripts that can be embedded into either a kickstart script or executed manually. The script will automatically perform the above operations above as well as configure the Virtual Flash Resource without any user input/intervention.

The main script is called configurevFRC.sh which is a shell script that performs the majority of the work and it then it calls the python script which is called addVirtualFlashResource.py (ensure you change the password variable in the script) for adding the Virtual Flash Resource. You need to download both scripts and run them on the ESXi Shell.

Here is the contents of configurevFRC.sh (you can download both scripts using the links above):
Here is a sample execution of configurevFRC.sh script:

In the future I hope we can completely automate vFRC configurations from the command-line as we can using the vSphere Web Client or vSphere APIs. For now, this solution will help get you around the limitations we have in the command-line utilities.

HostConfigureVFlashResource

2gbsparse Disk Format No Longer Working On ESXi 5.1

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I was recently made aware of an issue with my ghettoVCB script that after upgrading to ESXi 5.1, the ability to clone (or in this case backup) using the 2gbsparse disk format with vmkfstools was no longer working. The error that users were seeing was "The system cannot find the file specified." and I also confirmed this behavior by manually creating a VMDK and then trying to clone using the 2gbsparse format.

To give you some background, the 2gbsparse disk format is not a VMFS virtual disk format, it is part of the hosted desktop product (VMware Fusion, Workstation, Server & Player) disk format. This disk format was created to prevent cross-platform file system compatibility issue as pointed out in this VMware KB article. This issue does not exists on VMFS and hence this extra disk format is not necessary.

After some investigation, I found to use the 2gbsparse format in vmkfstools, you will need to load a specific VMkernel module called "multiextent". 2gbsparse was never officially supported on ESXi, you can not run a virtual machine with 2gbsparse disk format on ESXi and that is why a conversion maybe required when moving from a hosted product to ESXi. So by disabling unnecessary VMkernel modules that were not used made sense to help reduce amount of resources needed to load up. This is especially important with stateless deployments, where you want your ESXi host to load up as fast as possible.

Once you have enabled this VMkernel module, the 2gbsparse format will function again with vmkfstools. I also found that this was mentioned in the vSphere 5.1 release notes (yes, you should read the release notes)

To load the multiextent VMkernel module, run the following ESXCLI command:

esxcli system module load -m multiextent

To check whether the multiextent VMkernel module has loaded, run the following ESXCLI command:

esxcli system module list | grep multiextent

If you wish to persist this configuration after a system reboot, I found that you need to add the following command in a start-up script /etc/rc.local.d/local.sh as just setting the "enabled" flag is not sufficient for this particular VMkernel module.

localcli system module load -m multiextent

Note: We are using localcli because hostd may not be completely ready and you can either add a sleep/timer or just use localcli.

How to Create an SE Sparse (Space-Efficient) Disk in vSphere 5.1

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You probably may have heard, that with the upcoming release of vSphere 5.1, a new virtual machine disk format will be introduced called called SE Sparse (Space-Efficient). One of it's features is to provide the ability to reclaim unused blocks from within the guestOS. I would highly recommend you check out a recent blog post vSphere 5.1 Storage Enhancements – Part 2: SE Sparse Disks by Cormac Hogan for more details about the new SE Sparse disk format as well as other storage improvements in vSphere 5.1.

As Cormac points out, this new disk format will initially be leveraged by VMware View (in a future release from my understanding), as there are additional integrations required to use this feature than just using the new SE Sparse disk format. Having said that, the SE Sparse disk format is a feature of the vSphere 5.1 platform and with that, you do have the ability to create an SE Sparse disk.

Disclaimer: This is for educational purposes only, this is not officially supported by VMware. Please test this in a development environment before using it on actual systems.

There are two methods in which you can create an SE Sparse disk, directly on the ESXi Shell of an ESXi 5.1 host or remotely connecting to an ESXi 5.1 host.

Option 1 - Using vmkfstools on ESXi Shell 

Though it may not be documented, you can easily create a new VMDK with the new SE Sparse disk format by running the following command (10GB disk in this example):

vmkfstools -c 10g -d sesparse WindowsXP.vmdk

Here is a screenshot of new SE Sparse disk descriptor file to prove we have successfully created a new VMDK using the new format:

Option 2 - Using vSphere 5.1 API w/modified remote version of vmkfstools

As mentioned, the SE Sparse disk format is a feature of the vSphere 5.1 platform and as so, you can also leverage the vSphere 5.1 API to create a new VMDK using the virtualDiskManager and specifying the new SeSparseVirtualDiskSpec.

Note: Even though the vSphere API reference mentions the ability to set grain size via grainSizeKb property, I have found that it is not possible and just leaving it blank will automatically default to 1024K (1MB) which might be a system default for now.

You can download the modified version of the remote vmkfstools called vmkfstools-lamw which requires the the installation of vCLI 5.1 or vMA 5.1.

Here is an example of creating the same 10GB VMDK using the new SE Sparse disk format:

./vmkfstools-lamw --server 172.30.0.187 --username root -c 10G -d sesparse "[datastore1] WindowsXP.vmdk"

After you have created your new SE Sparse disk, the next logical step is assign it to a virtual machine. Since this is a new feature in vSphere 5.1, you will need to use the new vSphere Web Client to perform the operation as the legacy vSphere C# Client is not aware of this new disk type. You will also need to ensure that the virtual machine is running the latest ESXi 5.1 compatibility and later (virtual hardware version 9).

Once you have added our newly created disk from the datastore, it should now show up in the vSphere Web Client as Flex-SE for the disk type.

Additional Resources: