vmdk

Updates to VMDK partitions & disk resizing in VCSA 6.5

11.07.2016 by William Lam // 9 Comments

Similiar to the vCenter Server Appliance (VCSA) 6.0 release, the new VCSA 6.5 is also composed of multiple virtual machine disks (VMDKs). Each VMDK maps to a specific function and OS partition within the VCSA. There are now a total of 12 VMDKs, two of which are new in vSphere 6.5: vSphere Update Manager (VUM) and Image Builder. The following table provides a break down of the VMDKs in VCSA 6.5 compared to VCSA 6.0:

Disk	6.0 Size	6.5 Size	Purpose	Mount Point
VMDK1	12GB	12GB	/ and Boot	/ and Boot
VMDK2	1.2GB	1.8GB	VCSA's RPM packages	N/A as it is not mounted after install
VMDK3	25GB	25GB	Swap	SWAP
VMDK4	25GB	25GB	Core	/storage/core
VMDK5	10GB	10GB	Log	/storage/log
VMDK6	10GB	10GB	DB	/storage/db
VMDK7	5GB	15GB	DBLog	/storage/dblog
VMDK8	10GB	10GB	SEAT (Stats Events and Tasks)	/storage/seat
VMDK9	1GB	1GB	Net Dumper	/storage/netdump
VMDK10	10GB	10GB	Auto Deploy	/storage/autodeploy
VMDK11	N/A (Previously InvSrvc 5GB)	10GB	Image Builder	/storage/imagebuilder
VMDK12	N/A	100GB	Update Manager	/storage/updatemgr

In addition to the VMDK/partition changes, there are a couple of enhancements when needing to increase disk capacity in the VCSA. Just like in VCSA 6.0, you will still be able to hot-extend any one of the VMDKs while the system is still running.

The first change is that instead of the old vpxd_servicecfg command which is used expand the logical volume(s) making the new storage capacity available the OS/application, it has been replaced with the following command: /usr/lib/applmgmt/support/scripts/autogrow.sh
The second change is that instead of having to perform the above command using only SSH which may be disabled by default. There is now a new Virtual Appliance Management Interface (VAMI) REST API that can be called remotely: POST /appliance/system/storage/resize
The final difference is that in previous releases, you could only resize the Embedded VCSA or External VCSA node, but not the Platform Services Controller (PSC) node. In 6.5, this has changed and you can apply this method on any one of the VCSA nodes. Thanks to Blair for reminding me on this one!

Lets walk through an example of increasing the Net Dumper partition (VMDK9) and exercising this new VAMI API.

Step 1 - Login to VCSA using SSH to run a quick "df -h" to check the current size of your Net Dumper partition which by default will be 1GB as seen in the screenshot below.

Step 2 - Next, we will increase the VMDK to 5GB. In this example, I am using the vSphere Web Client but if you wanted to completely automate this process end-to-end, you can use the vSphere API/PowerCLI to perform this operation.

Step 3 - To quickly try out the new VAMI API, we will use the new vSphere API Explorer that is included in the VSCA 6.5. Simply open a web browser and enter the following URL: https://[VCSA-HOSTNAME]/apiexplorer Select the "appliance" API and then click on the login button and enter your vCenter Server credentials.

Step 4 - Scroll down to the POST /appliance/system/storage/resize operation and expand it. To call this API, just click on the "Try it out" button. If the operation completely successfully, you should see a 200 response as shown in the screenshot below.

Step 3 and 4 can also be called directly through PowerCLI using the new CIS cmdlets (Connect-CisServer & Get-CisService) which exposes the new VAMI APIs. Below is a quick snippet that performs the exact same operation:

Connect-CisServer -Server 192.168.1.150 -User *protected email* -Password VMware1!
$diskResize = Get-CisService -Name 'com.vmware.appliance.system.storage'
$diskResize.resize()

Step 5 - Lastly, we can now log back into the VCSA and re-run the "df -h" command to verify we can see the new storage capacity.

New method of enabling Multiwriter VMDK flag in vSphere 6.0 Update 1 (UI + API)

10.19.2015 by William Lam // 21 Comments

Prior to vSphere 6.0, in order for multiple Virtual Machines to share a VMFS-backed VMDK, the Multiwriter VMDK flag must be enabled, which is accomplished by adding a specific VM Advanced Setting as shown in this VMware KB 1034165. For customers who were accustomed to this old method, you may have found that this option no longer works. This was true regardless if you had used the vSphere Web/C# Client or the vSphere API to apply the configuration.

To provide for a better user experience, this behavior was changed in vSphere 6.0 and a new API was introduced for enabling and disabling the Multiwriter VMDK flag. In vSphere 6.0, there is now a new sharing attribute on the Virtual Disk backing property which accepts one of two values: sharingMultiWriter or sharingNone for specifying the Multiwriter flag. In my opinion, this is a positive change as we too often rely on the VM Advanced Setting as a generic "catch all" for enabling or configuring various settings versus adding proper APIs to a VM.

Although there is now a proper API which will can help enable new Automation use cases, one thing that was still lacking was an easy way to enable the Multiwriter VMDK flag using the UI. In vSphere 6.0 Update 1, we have now introduced a new UI dropdown option called "sharing" in the vSphere Web Client for configuring the Multiwriter VMDK flag which can be found in the Virtual Disk section when editing a VM as shown in the screenshot below.

Note: The new Sharing property is only available in the vSphere Web Client UI and is not available in the vSphere C# Client. If you need to configure the Multiwriter VMDK flag and do not have access to the vSphere Web Client, you can use the vSphere API to help automate this configuration change.

UPDATE (06/27/16) - Created two scripts which now cover scenarios where VM is online and/or offline.

For those interested in Automating the Multiwriter VMDK flag, I have created two PowerCLI scripts called: configureMultiwriterVMDK.ps1 (offline VM configuration) and addMultiwriterVMDK.ps1 (online VM configuration) which demonstrates this new vSphere API.

The first script configureMultiwriterVMDK.ps1 allows you enable the Multiwriter Flag for an existing VMDK that has already been added to a VM. This operation must be done while the VM is powered off and to use the script you will need to specify the name of the VM as well as the label of the VMDK in which you wish to enable the Multiwriter VMDK flag (e.g. Hard disk 2). Below is an example of running the script.

The second script addMultiwriterVMDK.ps1 allows you to hot-add a new VMDK and enables the Multiwriter Flag to a VM. This operation is done while the VM is powered on which is a common workflow for customers needing to hot-add storage to an existing Cluster solution such as Oracle RAC for example all while the system is running. To use the script, there are a few variables you will need to edit:

vmName - The name of the VM you wish to perform th operation on
vmdkFileNamePath - This is the full datastore path to the name of the underlying VMDK. See the script for more information but the syntax will look like "[datastore-name] vm-home-dir/vmdk-name.vmdk"
diskSizeGB - The capacity of the VMDK to add (GB)
diskControllerNumber - The SCSI controller number (0-3)
diskUnitNumber - The Unit number (0-16)

Multiple VMDKs in VCSA 6.0?

03.09.2015 by William Lam // 10 Comments

One thing you might notice after deploying the new VCSA 6.0 is that it now includes 11 VMDKs. If you are like me, you are probably asking why are there so many? If you look at past releases of the VCSA, it only contained two VMDKS. The first disk was used for both the OS and the various VMware applications like vCenter Server, vSphere Web Client, etc. and the second disk was where all the application data was stored such as the VCDB, SSODB, Logs, etc.

There were several challenges with this design, one issue was that you could not easily increase the disk capacity for a particular application component. If you needed more storage for the VCDB but not for your logs or other applications, you had no choice but to increase the entire volume. In fact, this was actually a pretty painful process because a logical volume manager (LVM) was also not used. This meant that you needed to stop the vCenter Server service, add a new disk, format it and then copy all the data from the old volume to the new. Another problem with the old design is that you can not apply Storage QoS on important data such as the VCDB which you may want on a faster tier of storage or putting your Log data on slower and cheaper tier of storage by leveraging something like VM Storage Policies which works on a per VMDK basis.

For these reasons, VCSA 6.0 is now comprised of 11 individual VMDKs as seen in the screenshot below.

Here is a useful table that I have created which provides the mappings of each of the VDMKs to their respective functions.

Disk	Size	Purpose	Mount Point
VMDK1	12GB	/ and Boot	/ and /boot
VMDK2	1.2GB	Temp Mount	/tmp/mount
VMDK3	25GB	Swap	SWAP
VMDK4	25GB	Core	/storage/core
VMDK5	10GB	Log	/storage/log
VMDK6	10GB	DB	/storage/db
VMDK7	5GB	DBLog	/storage/dblog
VMDK8	10GB	SEAT (Stats Events and Tasks)	/storage/seat
VMDK9	1GB	NetDumper	/storage/netdump
VMDK10	10GB	AutoDeploy	/storage/autodeploy
VMDK11	5GB	Inventory Service	/storage/invsvc

In addition, increasing disk capacity for a particular VMDK has been greatly simplified as the VCSA 6.0 now uses LVM to manage each of the partitions. You can now, on the fly increase disk space for a particular volume while the vCenter Server is still running and the changes will go live immediately. You can refer to this article here for the process as it is a simple two step process.

Here are some useful commands to get more details of the filesystem structure in the new VCSA.

lsblk

lsscsi