How is Horizon View configured for VMware VSAN?

In my previous article I discussed VSAN benefits for Horizon View (How does VMware VSAN help Horizon View?), including CAPEX and OPEX savings provided by the use of inexpensive server disks for shared storage and simplified day-to-day storage configuration and provisioning activities.

In this article I will explore some of the VSAN capabilities and features and how they relate to Horizon View.

VSAN has interesting capabilities that are surfaced by the VASA storage provider (vSphere Storage APIs for Storage Awareness). VASA, is a set of APIs that permits storage arrays to integrate with vCenter for better management functionalities, such as discovery of storage and LUN capabilities, capacity and storage health monitoring. The Storage Policy Based Management (SPBM) within VSAN manages these VASA functionalities.

In Horizon View, the View Composer Service is the component responsible for automatically setting the VSAN storage policy profile when creating a linked clone pool, rebalancing or performing a recompose operation. Find more about linked clone operations in my article VMware View 4.5 Linked Cloning explained.  Please note that VSAN storage policies are also supported for Full Clones.

The main parameters that VSAN exposes on a per-object basis are as follows:

• Number of Disk Stripes Per Object: Defines the # of physical disks across which each copy of a storage object is striped. The higher the value, the higher the performance (throughput and bandwidth) but the more disks that you need.
• Number of Failures To Tolerate: Defines the # of hosts and/or disk failures that can be tolerated. For ‘n’ failures, ‘n’ + 1 copies of an object are created.
• Object Space Reservation: Defines the percentage of the logical size of the storage object that should be reserved during initialization.
• Flash Read Cache Reservation: Defines the percentage of the logical size of the storage object that should be reserved as a read cache from the flash capacity.

For detailed information on storage policies read Cormac’s article VSAN Part 7 – Capabilities and VM Storage Policies.

In a VSAN deployment each object receives a set of storage policies. These policies are commonly setup by the vSphere administrator, but in Horizon View they are pre-set with specific values.

Replica Disk Profile: The Linked Clone Replica is created for each new desktop pool in each datastore and it’s based on the snapshot in use at any given desktop pool. In scenarios where Horizon View Storage Tiering is enabled a single replica per pool is created.

• Disk Stripes: 1
• Failures to Tolerate: 1
• Object Space Reservation: 0
• Flash read cache reservation: 10%

1. There is a differentiation between profiles for persistent and floating pools when combined with Linked Clones However, for floating pools the Failures to Tolerate is set to 0.
2. The replica disk object is created during provisioning and will not grow afterwards, so there is no need for object space reservation.
3. In our performance tests we have identified that 10% Flash read cache is be sufficient to handle most VDI working set sizes.

Linked Clone Disk Profile: Linked clone is a chain of delta disks that track the differences between the original and the clone.

• Disk Stripes: 1
• Failures to Tolerate: 1
• Object Space Reservation: 100
• Flash read cache reservation: 0%

Persistent Disk Profile: This is the old User Data Disk that has been renamed. It is still possible to store the persistent disk within the Guest OS disk, or in a separate disk.

• Disk Stripes: 1
• Failures to Tolerate: 1
• Object Space Reservation: 100
• Flash read cache reservation: 0%

For detailed information on Linked Clone disk types read VMware View 4.5 Linked Cloning explained.

Full Clone Disk Profile: This is the policy profile to be applied to all the VM disks for a full clone.

• Disk Stripes: 1
• Failures to Tolerate: 1
• Object Space Reservation: 100
• Flash read cache reservation: 0%

1. There is a differentiation between full clones when used with floating pools. In this case the option Failures to Tolerate is set to 0.

Horizon View automatically creates the profiles listed above in vCenter Server and it will preserve these profiles during upgrade if they already exist. Administrators can create their own policy profiles and Horizon View will not modify or delete these profiles.

VSAN storage policies will be automatically set during the pool wizard ensuring that the policy is applied appropriately when a refresh or recompose operation is triggered. For rebalance there will be support for VSAN to non-VSAN datastores or vice-versa, but pools cannot span both VSAN and non-VSAN datastores. This restriction is enforced by Horizon View.

In my next article I will explore the importance of Content-Based Read Cache (CBRC) in Horizon View with VSAN deployments.

This article was first published by Andre Leibovici (@andreleibovici) at myvirtualcloud.net.