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VDI design considerations

7 Dell EMC SC Series: 3,000 VMware Horizon Linked Clone VDI Users | 4735-RA-V

1.5 Storage pools

In general, it is recommended to use fewer storage pools within SC Series arrays because this reduces

complexity and increases flexibility, and usually improves performance. Dell EMC recommends using a single

disk pool for hosting VDI desktop volumes. This provides better performance by leveraging the aggregate I/O

bandwidth of all disks to service I/O requests from the VMware ESXi™ hosts. A single drive pool also allows

all hosts to share the volumes enabling VMware vSphere Storage vMotion

. This enables hosts to go into

maintenance mode and VMs to be moved without taking an outage. This greatly simplifies host updates and

patches.

A single storage pool also allows all storage to be available for all services. Since snapshots and replication

use the same pool, having all storage available in a single pool means all services have access to the entire

storage array. If there are requirements for latency or bandwidth thresholds to be defined, QoS and latency

priorities can be defined per volume.

1.5.1 RAID configurations

By default, SC Series storage uses the RAID 10 protection level when creating new pages within a storage

pool. The I/O requirements for VDI desktops need to be clearly defined to size the storage correctly. As data

becomes less active, it is moved to RAID 5 or 6, depending on the activity level.

The small footprint and high I/O density typically allows a smaller drive size, reducing drive rebuild times. This

means RAID 5 is preferred over RAID 6 in most cases. The choice of RAID 5 or 6 is based on drive size and

rebuild time requirements.

1.6 Validating the storage design

VDI workloads can be challenging to simulate. They consist of hundreds to thousands of virtual machines,

making it difficult to recreate the load. There are few tools that can accurately simulate this.

consistent manner.

To accurately simulate the storage load, the following needs to be performed:

• Create the base image to match the intended configuration

• Simulate the correct user count

• Run the applications as a user would

• Determine the optimum number of volumes based on recovery requirements and management

overhead

• Create a baseline for the number of I/Os and GBs per user to determine the storage requirements

1.6.1 Validating the I/O path

VDI workloads tend to be fairly small block. The average I/O size is between 24k and 32k. The number of I/Os

generated are fairly high due to the number of users per volume.

Spreading users across more volumes typically does not affect SC Series array performance. Using 20 to 30

volumes can support 3,000 users. For a smaller number of users, fewer volumes can be used. More volumes

require additional management effort, but spread the I/O across more LUNs for better performance. This also

results in smaller volumes for recovery or replication purposes.