How to: Claiming Disk for vSAN

On Monday’s post, I did a quick blog on how easy it was to enable vSAN within vCenter. vSAN, as it was discussed in earlier posts,  is a very powerful tool that utilizes software defined storage at the hypervisor level, which reduces costs and complexity. Storage is the key ingredient to this solution, so we may need to add disk in order to actually utilize vSAN right?  Fortunately, VMware (like most things with vSAN) has made this process incredibly simple. Today’s blog is a continuation from Monday’s blog, which will show us how easy it is to claim disk for vSAN usage. Disk claiming is needed in order build out your vSAN datastore. This is what makes vSAN so different from traditional hosts/storage configurations.

*Note: Each of my hosts have already met the minimum vSAN requirements. Before proceeding you will need to ensure you have a vSAN cluster with at least three ESXi hosts with two disk each, one for cache and one for capacity.

Login to vCenter, then select your vSAN cluster and click on configure. Next, locate “Disk Management” under Virtual San. Select the hard disks icon with black checks underneath the word “Disk Groups”.


You are now presented with the option to claim disk. Remember, you must have at least one drive for cache and one drive for capacity.


  1. Since this is a test lab, you can mark disk as flash (you wouldn’t want to do this in a production environment).
  2. In order to mark a disk and Flash, select the disk and hit the icon with the “F” in the center.
  3. Now that the drive has been marked as flash, we can claim each disk for the cache tier. In order to do this, select each disk and hit the hard disk with the “lightening blot”, which is on the far left.
  4. You show now show what this windows shows, each 40GB drive is marked as Flash, and each disk has been claimed for the cache tier.


  1. Next, we are going to repeat this steps by marking each 150GB drive as HDD and claim them for the capacity tier.
  2. To accomplish this, select each disk and hit the small icon that has “HDD” on it.
  3. Once each disk as been marked as “HDD” we can claim them for the capacity tier.
  4. Next, select each disk and click the icon with the “storage cylinders on top”. This is to the far left, to the right of the “lighting bolt”.
  5. Finally, select OK to continue to finalize.


The recent task should show the host marking the disk as a flash disk and hard disk, etc.


The cluster continues to configure the disk devices.


Once that has completed, head back to your vSAN cluster and go to summary to see your vSAN datastore capacity.

Hold up! Issue? I was greeted with a warning that “Virtual SAN datasore vsanDatastore in cluster vSAN in datacenter Virtualboi does not have capacity”. I clicked on disk management to see why.


I can see that the disk groups all look healthy. What could be the problem? Oh that’s it, Maintenance mode! I had forgotten each of my hosts were in maintenance mode.

*Note, this is one of the many differences with vSAN. Since the storage is local, placing a host in maintenance mode DOES impact storage availability. Since this was the initial setup, there was no impact; however, placing vSAN hosts in maintenance mode can have impacts on data availability, and it’s important to understand the different types of data evacuation methods. For more information, check this link.


Once I exited maintenance mode on each hosts, my vsanDataStore showed no issues and I was able to see my capacity just fine. Now all that’s needed is for some VMs to be deployed!



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