Storage configuration is essential for any successful database deployment, especially in virtual environments where you can consolidate many different database workloads on a single ESXi host. Your storage subsystem should provide sufficient I/O throughput as well as storage capacity to accommodate the cumulative needs of all database virtual machines (DBVMs) running on your ESXi hosts.

Data Director allows you to define virtual disks to which you can map your DBVM's operating system, data, log, and backup disks. You can then map the virtual disks to different datastores using disk provisioning and storage allocations that you specify to improve disk usage, performance, and redundancy. For example, you can create dedicated datastores to service I/O intensive database workloads.

VMware storage virtualization can be categorized into three layers of storage technology.

The storage array is the bottom layer, consisting of physical disks presented as logical disks in the form of either storage array volumes or logical unit numbers (LUNs) to the layer above.

The next layer is the virtual environment occupied by vSphere. Storage array LUNs are presented to ESXi hosts as datastores and are formatted as VMFS volumes.

Virtual machines consist of virtual disks that are created in the datastores and presented to the guest operating system as disks that can be partitioned and used in file systems.

VMFS is a cluster file system that provides storage virtualization optimized for virtual machines. Each virtual machine is encapsulated in a set of files and VMFS is the default storage system for these files on physical SCSI disks and partitions. VMFS allows multiple ESXi instances to access shared virtual machine storage concurrently. It also enables virtualization-based distributed infrastructure services such as vMotion, DRS, and VMware HA to operate across a cluster of ESXi hosts.

A generally accepted best practice is to create a dedicated datastore if an application has a demanding I/O profile. Databases fall into this category. The creation of dedicated datastores allows you to define individual service level guarantees for different applications, and is analogous to provisioning dedicated LUNs in a physical server environment.

Aligning file system partitions is a well-known storage best practice for database workloads. Partition alignment on both physical machines and VMware VMFS partitions prevents I/O performance degradation caused by I/O crossing track boundaries. Using the vSphere Client to create VMFS partitions avoids this problem since, beginning with ESXi 5.0, it automatically aligns VMFS3 or VMFS5 partitions along the 1MB boundary.

When creating partitions VMware recommends the following best practices:

Create VMFS partitions from within vCenter because they are aligned by default

Align the data disk for heavy I/O workloads using diskpart.

Consult with the storage vendor for recommendations on how best to use their hardware in conjunction with your Data Director deployment.