6.0.1

Table Of Contents
Initial Placement and Ongoing Balancing
Storage DRS provides initial placement and ongoing balancing recommendations to datastores in a Storage
DRS-enabled datastore cluster.
Initial placement occurs when Storage DRS selects a datastore within a datastore cluster on which to place a
virtual machine disk. This happens when the virtual machine is being created or cloned, when a virtual
machine disk is being migrated to another datastore cluster, or when you add a disk to an existing virtual
machine.
Initial placement recommendations are made in accordance with space constraints and with respect to the
goals of space and I/O load balancing. These goals aim to minimize the risk of over-provisioning one
datastore, storage I/O bottlenecks, and performance impact on virtual machines.
Storage DRS is invoked at the configured frequency (by default, every eight hours) or when one or more
datastores in a datastore cluster exceeds the user-configurable space utilization thresholds. When Storage
DRS is invoked, it checks each datastore's space utilization and I/O latency values against the threshold. For
I/O latency, Storage DRS uses the 90th percentile I/O latency measured over the course of a day to compare
against the threshold.
Storage Migration Recommendations
vCenter Server displays migration recommendations on the Storage DRS Recommendations page for
datastore clusters that have manual automation mode.
The system provides as many recommendations as necessary to enforce Storage DRS rules and to balance
the space and I/O resources of the datastore cluster. Each recommendation includes the virtual machine
name, the virtual disk name, the name of the datastore cluster, the source datastore, the destination
datastore, and a reason for the recommendation.
n
Balance datastore space use
n
Balance datastore I/O load
Storage DRS makes mandatory recommendations for migration in the following situations:
n
The datastore is out of space.
n
Anti-affinity or affinity rules are being violated.
n
The datastore is entering maintenance mode and must be evacuated.
In addition, optional recommendations are made when a datastore is close to running out of space or when
adjustments should be made for space and I/O load balancing.
Storage DRS considers moving virtual machines that are powered off or powered on for space balancing.
Storage DRS includes powered-off virtual machines with snapshots in these considerations.
Create a Datastore Cluster
You can manage datastore cluster resources using Storage DRS.
Procedure
1 Browse to Datacenters in the vSphere Web Client navigator.
2 Right-click the datacenter object and select New Datastore Cluster.
3 Follow the prompts to complete the New Datastore Cluster wizard.
4 Click Finish.
vSphere Resource Management
92 VMware, Inc.