4. Resource Group Architecture : 4.3 Storage Resources : 4.3.5 vSphere Storage DRS
4.3.5 vSphere Storage DRS
vSphere Storage DRS provides initial placement and on-going balancing recommendations for datastores in a vSphere Storage DRS-enabled datastore cluster. A datastore cluster represents an aggregation of datastore resources, analogous to clusters and hosts.
*vCloud Director 5.1 supports vSphere Storage DRS when using vSphere 5.1 hosts. vSphere Storage DRS also supports fast provisioning (linked clones) in vCloud Director 5.1.
*vSphere Storage DRS continuously balances storage space usage and storage I/O load, avoiding resource bottlenecks to meet service levels and increase manageability of storage at scale.
*vCloud Director 5.1 recognizes storage clusters. The member datastore clusters are visible in vCloud Director, but cannot be modified from vCloud Director.
*vCloud Director 5.1 utilizes vSphere Storage DRS for initial placement of virtual machines.
*vCloud Director uses vSphere Storage DRS to manage space utilization and I/O load balancing. vSphere Storage DRS can help rebalance virtual machines, media, and virtual machine disks within the storage pod.
*As in vCloud Director 1.x, vCloud Director 5.1 determines optimal placement between datastore clusters and standalone datastores across all vSphere instances assigned within vCloud Director.
*There is a new VIM object type in the REST API named DATASTORE_CLUSTER. The datastore properties now include the member datastore list when the VIM object type is DATASTORE_CLUSTER. vSphere Storage DRS and Fast Provisioning
*vSphere Storage DRS supports fast provisioning in vCloud Director.
*vSphere Storage DRS supports linked clones only with vCloud Director 5.1.
*Linked clone configurations that span across datastores are not supported in vCloud Director 5.1.
*vSphere Storage DRS will not recommend placement of a linked clone that would span datastores from the base disk.
*vSphere Storage DRS will migrate a clone to a datastore containing a shadow virtual machine and relink the clone to the existing shadow virtual machine.
*Linked clones can be migrated between VMFS3 and VMFS5 and are supported in vSphere Storage DRS. The format conversions are handled automatically at the platform level.
*The logic for migrating a virtual machine is influenced by factors such as the following:
*Amount of data being moved.
*Amount of space reduction in the source datastore.
*Amount of additional space on the destination datastore.
*Linked clone decisions also depend on whether the destination datastore has a copy of a base disk or whether a shadow virtual machine must be instantiated:
*Putting a linked clone on a datastore without the base disk results in more space used on the datastore as opposed to placing the clone on a disk where a shadow virtual machine already exists.
*During the initial placement, vSphere Storage DRS selects a datastore that contains a shadow virtual machine so that placement results in maximum space savings. If necessary, initial placement recommendations can include evacuating existing virtual machines from the destination datastore.
*If a datastore that already contains the base or a shadow virtual machine is not available, vCloud Director makes a full clone to create a shadow virtual machine in a selected datastore, and then makes linked clones in the selected datastore.
*The latest model in vSphere Storage DRS takes linked clone sharing into account when calculating the effects of potential moves.
*Linked clones and virtual machines that are not linked clones can reside on the same datastores. vSphere Storage DRS Limitations
*vCloud Director does not support creation, deletion, or modification of storage pods. These tasks must be performed at the vSphere level.
*vCloud Director does not support member datastore operations.
*Enabling vSphere Storage DRS for the datastore clusters used with vCloud Director is not supported if vSphere hosts are pre-vSphere 5.1.