vCD SP 8.10 New Features Part 3 – Storage Tiering and Storage Management

vCloud Director SP 8.10 has been out for a couple months now and the general buzz around this release has been extremely positive. The decision to expose the previously API only features has been warmly welcomed by most vCloud Air Network Service Providers and I have heard of quiet a few looking to deploy or plan deployment of vCD SP 8.10 into their hosting platforms.

In Part One I went through the new NSX supportability improvements and in Part Two I went through the tenant ability to configure VM affinity and anti-affinity rules. In Part Three I am going to go through something that’s been available via the API since vCD 5.6.3 SP but is now exposed via the UI and also take a look at a new feature around the limiting of the max size of a tenant VMDKs in a vCD environment.

  • VM Disk Level Storage Profiles – Allows a single virtual machine (VM) to access different tiers of storage such as storage area network (SAN), network-attached storage (NAS), and local storage to help balance storage cost vs. storage performance. VMware vCloud Director 5.6 also supports VMware Virtual SAN.

Fast Provisioning:

Before showing the new UI Storage Profile features it’s worth mentioning that this will not work if you have vDCs configured with fast provisioning enabled. If you try to configure multiple profiles against a VM you will get a “Cannot use multiple storage profiles in a fast-provisioned VDC” error message.

Fast provisioning was introduced with vCloud Director 1.5 and enables speeding up a cloning process when deploying vApps from catalog or copying VMs. It utilizes vSphere linked clones where the base image is not cloned, instead a delta disk is created to record changed blocks.

Great in theory, but also carries some caveats…not allowing VM Disk level storage profiles being one of them. If turned on, head to the Storage Tab of the vDC and uncheck the option as shown below.

VM Disk Level Storage Profiles:

There isn’t a lot that needs explaining in terms of what can now be achieved through the UI to better provision and manage different storage requirements on a per VM disk basis. vCD Storage Profiles directly plug into vCenter Storage Policies and inherit the characteristics passed through from vCenter into vCD via the Provider vDC. These are then allocated to vDCs as shown in the image above. Generally speaking these policies map back to different tiers of storage and allow the Service Provider to offering different service levels at different price points.

As an example a tenant may have a requirement to have a large file server that doubles as a Domain Controller (it happens more than you think) for the System drive the requirements might state that you need SAS backed storage and SATA backed for a secondary volume. This can now be achieved through the vCD UI as shown below.

You can see above that Disk 0 is on ioSTOR-500 and Disk 1 is on ioSTOR-250. The example above is for the adding of new disks to a VM…you can also change the Storage Profile while a VM is on. This will trigger a Storage vMotion in the background if required as shown below.

Limiting Maximum Disk Size:

There are some scenarios where a Service Providers might want to limit the max size of tenant VMDKs in order to comply with capacity planning requirements or storage level constraints. The current max size for a VMDK in vSphere is 62TB and being realistic there are not too many Service Providers out there who provision datastores that size. Typically, the storage limits applied at an allocation pool should limit the creation of stupidly large disks by tenants, but there is the possibility that someone with deep pockets purchasing large amounts of storage could try to provision a VM (thin or not) Disk larger than the datastores underpinning the storage policy.

To set the global disk limit you use the cell-management-tool command on any vCD cell in the instance. Once run the value is honors immediately and without restart of the vCD services as shown in the example below that limits the disks to 500GB.

./cell-management-tool manage-config -n vmlimits.disk.capacity.maxMb -v 500000

Once configured, if a tenant tries to provision a disk bigger than the limit they will get an error stating that the “Requested disk size exceeds maximum allowed capacity“.