VMware vSphere® Storage DRS™ continuously balances storage space usage and storage I/O load while avoiding resource bottlenecks to meet application service levels. Using Storage DRS allows you to:
- Deploy and integrate additional storage capacity to a storage pool.
- Take advantage of new capacity.
- Improve service levels for all applications.
- Increase VMware vSphere® administrator productivity by allowing them to monitor and manage additional infrastructure.
Storage DRS monitors storage space and I/O utilization across a pre-assigned datastore pool and aligns storage resources to meet your business growth needs. Storage DRS monitoring allows you to:
- Specify how storage resources are allocated to virtual machines with rules and policies.
- Assign dedicated storage infrastructure to business units while achieving higher storage utilization through storage volume pools.
- Empower business units to build and manage virtual machines within their storage pools while providing IT control over all storage resources.
When a vSphere administrator places a Storage DRS-enabled datastore cluster in Maintenance Mode, Storage DRS moves virtual machine disk files to another datastore. A datastore remains in Entering Maintenance Mode state until all virtual disks have moved to other data stores within the cluster. Storage DRS also features:
- Placement recommendations where virtual disks can be migrated
- A list of faults that displays virtual machine disk files that cannot be moved and the reasons why
vSphere 5.5 introduced a new VMware® vCenter Server™ object called a datastore cluster, which is a collection of datastores aggregated into a single unit of management and consumption. When you create a datastore cluster, Storage DRS can manage storage resources comparable to how VMware vSphere® Storage vMotion® DRS manages compute resources within a cluster.
Storage DRS makes initial placement recommendations and decisions based on space constraints and I/O load. These recommendations minimize risks associated with improper placement of virtual machine disk images and reduce I/O bottlenecks and performance impacts on virtual machines. Storage DRS selects the best placement based on lowest latency and available space.
When one or more datastores in a datastore cluster exceeds the user-configurable space utilization or I/O latency thresholds, Storage DRS makes balancing recommendations. In automatic mode, Storage DRS makes Storage vMotion decisions to lower I/O latency to keep all virtual machines performing optimally. In manual mode, Storage DRS makes balancing recommendations that an administrator may approve.
Storage DRS evaluates I/O load every eight hours and makes recommendations based on the results. The maximum default I/O latency is 15 milliseconds and the default space utilization threshold is 80 percent.
You may optionally define affinity and anti-affinity rules for your virtual machine disk files. By default, virtual machines disk files are stored on the same datastore. Storage DRS offers three types of affinity rules that you may apply:
- VMDK Affinity (default) - Virtual disks of a virtual machine are kept together on the same datastore.
- VMDK Anti-Affinity - Virtual disks of a virtual machine with multiple virtual disks are placed on different datastores.
- VM Anti-Affinity - Two specified virtual machines, including associated disks, are placed on different datastores.
Datastore correlation is an advanced I/O load balancing mechanism in Storage DRS that discovers when two distinct datastores are using the same set of disk spindles on an array. When this occurs, it applies affinity rules and moves virtual machine disk files to relieve I/O bottlenecks.