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How To Initiate a Wipe & Shrink Operation On an SE Sparse Based Disk

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In my previous two articles, I showed you how to create your own SE Sparse disks as well as creating new virtual machine Linked Clones leveraging the new SE Sparse disk format. If you recall earlier, one of the features of the SE Sparse disk format is to provide the ability to reclaim unused blocks within the guestOS which is a two step process: wipe and shrink.

Here is a screenshot that describes the process which was taken from the What's New In vSphere 5.1 Storage Whitepaper by my colleague Cormac Hogan. I highly recommend you check out the whitepaper which includes more details about this feature and other storage improvements in vSphere 5.1

The process of kicking off this wipe and shrink operation will be done through an integration with VMware View (a future release from my understanding). Now, it's important to understand that it's not just simply calling these two operations but it is also when they are called. The wipe operation is more CPU intensive as it scans for unused space within the guestOS filesystem and the shrink operation is more I/O intensive as it issues the SCSI unmaps commands. I can only assume that these operations will be scheduled based on the utilization of the guestOS to help reduce the impact to the VM workload.

Now having said that, since the SE Sparse disk format is a feature of the vSphere 5.1 platform, so are both the wipe and shrink operations. Though they are not exposed in the public vSphere API like the SE Sparse disk format, you can still access the private APIs if you know where to look 😉

Disclaimer: This is for educational purposes only, this is not officially supported by VMware. Use at your own risk.

With some help from my good friend the vSphere MOB and some digging, I have located the two vSphere API methods for wipe and shrink operation. Before getting started, ensure you have a VM with at least one SE Sparse disk, else these commands will not be very useful.

Note: In this experiment, I tested the wipe and shrink operation with Windows XP image, this may or may not work on other OSes.

First you will need to search for the VM in question and retrieve it's vSphere MOB URL which is in the format of https://[vcenter-server]/mob/?moid=vm-X where X is the MoRef ID for your VM. You can either navigate through the vSphere MOB or use my MoRef finder script.

Wipe Operation

To issue the wipe API, enter the following URL into your web browser (remember to replace the MoRef ID with the one of your VM)

https://[vcenter-server]/mob/?moid=vm-X&method=wipeDisk

Here is a screenshot of what that looks like if you are able to successfully access the private API:

Go ahead and click on "Invoke Method" which will then execute the wipe operation. If you take a look at the vSphere Web Client, you should now see a new task for the wipe operation.

This can take a bit of time as it scans through the guestOS filesystem for unused space.

Shrink Operation

Once the wipe operation as completed, we then need to issue the shrink API. Enter the following URL into your web browser (remember to replace the MoRef ID with tone of your VM)

https://[vcenter-server]/mob/?moid=vm-X&method=shrinkDisk

Here is a screenshot of what that looks like if you are able to successfully access the private API:

Here you can specify particular disks (requires diskId) that you wish to perform the shrink operation on. If you leave it blank, it will try to shrink all disks associated with your VM. In our example, I will shrink all disks. Go ahead and click on the "Invoke Method" which will kick off the shrink operation. If you go back to the vSphere Web Client, you should now see a shrink task in progress.

Again, this operation can also take some time, but once it has finished, then you have successfully reclaimed any unused blocks within your guestOS.

Enabling/Disabling EVC using the vSphere MOB

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There were some discussions this morning on twitter regarding the configuration of EVC for a vSphere Cluster using one of the vSphere CLI's such as PowerCLI or directly leveraging the vSphere API. Unfortunately, this is not possible today as the operations pertaining to EVC are not currently exposed in the vSphere API. This means you will not be able to use the vCLI, PowerCLI, vCO or the vSphere API to configure and manage EVC configurations, you will need to use the vSphere Client to do so.

Having said that, one could still "potentially" automate EVC configurations using the vSphere MOB interface using the private vSphere API, but it may not be ideal and will require some "creativity" and custom coding to integrate with your existing automation solution. This particular limitation of the vSphere API is one that I have personally faced and have filed a bug with VMware awhile back. I am hoping this will eventually be added to the public vSphere API, so that users can fully automate all aspects and configurations of a vSphere Cluster.

Disclaimer: This is not officially supported by VMware, use at your own risk and discretion.

Step 1 - Connect to your vCenter MOB and traverse to the vSphere Cluster of interest (note the MOID will be different in your specific cluster).

Step 2 -  Now replace the URL with the following while substituting the cluster MOID that you see in your browser:

https://reflex.primp-industries.com/mob/?moid=domain-c1550&method=transitionalEVCManager

and hit enter and you'll be brought to TransitionalEVCManager() method, you'll then want to click on the "Invoke Method". Once you do so, you should be returned with a task object and you'll have a link to something like evcdomain-cXXXX. Click on this and you'll be brought to ClusterTransitionalEVCManager.

Step 3 - From here you'll have have some basic evcState information which you can click on to see what the current EVC configuration is set to, guaranteedCPUFeatures and valid EVC Modes (the last part will be important for reconfiguring EVC)

Step 4 - Now let's say the cluster currently has EVC Mode set to intel-merom and you would like to change it to Nehalem, you would need to retrieve the key from the previous page, in our example it's intel-nehalem. Now, you need to click on the method link called ConfigureEVC_Task which is pretty straight forward, it just accepts the EVC Mode Key, enter the string and click on "Invoke Method" and now your cluster will be reconfigured if you go back to the evcState or look at your vCenter task. You can also disable EVC by using DisableEVC_Task

 
Note: If EVC is already configured in your vSphere Cluster, you can use the vSphere API to view it's current configuration by looking at the ClusterComputeResource's summary property. You just will not be able to make any changes or disabling EVC using the vSphere API.

Ghetto webAccess for ESXi

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I got the idea for this post a few months back after noticing several questions on the VMTN forums on how to enable webAccess for ESXi. With ESXi, the webAccess interface is no longer available as it was with classic ESX. After seeing the question and randomly browsing through the various flings on VMware Labs, I noticed an interesting fling called Ops Panel for ESX. Ops Panel provides a simple javascript that leverages the vSphere MOB to perform basic power operations for virtual machines and it is loaded onto the homepage of a classic ESX host remotely using Greasemonkey.

I immediately wondered if I could run the javascript directly on an ESX or ESXi host without the use of Greasemonkey. With a quick tweak of the default index.html homepage, I was able to get a simple "ghetto" webAccess running on both an ESX and ESXi host. I also ran into several bugs, one that dealt with how the power state of a virtual machines was being captured by the differences in the ESX(i) 4.0, 4.1 and 5.0 APIs and a recent fix to a CSRF (Cross-Site Request Forgery) vulnerability in ESX(i) 4.1 Update 1 that made it difficult to get Ops Panel running on more than just ESX(i) 4.0.

I reached out to the fling creator Ivan Donchev and he was kind enough to help assist me in the issues I ran into and also provided an updated version of his script to properly handle both the power state and the CSRF workaround. He recently published an update to his script a few weeks back supporting both ESX 4 and ESXi 5 but missed ESX(i) 4.1 support due to limited amount of testing. This was an easy fix and I modified the script to include support for ESX(i) 4.1 and also changed the default power off operation to a guestOS shutdown. The modified version of the script can be downloaded here.

When you browse to the homepage of your ESX(i) host using the browser, you will be prompted to login which require the same credentials as if you were to login to the host directly using the vSphere Client or vSphere MOB.

Once you have logged in, it will search for all virtual machines running on the host and generate the list of virtual machines and their respective power states.

You can then perform the appropriate power operation such as a power on, shutdown or suspend using the icons on the right. This can be really useful if you don't have access to vCenter Server, vSphere Client or SSH access to the host but just have a web browser.

To load the Ops Panel script on an ESX(i) host, you will need to do the following:

Note: These instructions are applicable for both ESX and ESXi, but with ESXi, it is important that the commands to copy both the modified index.html and Ops Panel script to docroot are executed as changes are not persisted after a reboot for ESXi hosts.

You can also add this to your kickstart file by appending the lines above in your %firstboot stanza so you automatically get Ops Panel after install. Though this will not give you a full webAccess that classic ESX did but it definitely is a useful way to quickly get to your virtual machines and perform simple power operations using a web browser.