vCenter Server places limits on the number of simultaneous virtual machine migration and provisioning operations that can occur on each host, network, and datastore.

Each operation, such as a migration with vMotion or cloning a virtual machine, is assigned a resource cost. Each host, datastore, or network resource, has a maximum cost that it can support at any one time. Any new migration or provisioning operation that causes a resource to exceed its maximum cost does not proceed immediately, but is queued until other operations complete and release resources. Each of the network, datastore, and host limits must be satisfied for the operation to proceed.

vMotion without shared storage, migrating virtual machines to a different host and datastore simultaneously, is a combination of vMotion and Storage vMotion. This migration inherits the network, host, and datastore costs associated with those operations. vMotion without shared storage is equivalent to a Storage vMotion with a network cost of 1.

Network Limits

Network limits apply only to migrations with vMotion. Network limits depend on the version of ESXi and the network type. All migrations with vMotion have a network resource cost of 1.

Table 1. Network Limits for Migration with vMotion
Operation ESXi Version Network Type Maximum Cost
vMotion 5.0, 5.1, 5.5, 6.0, 6.5, 6.7 1GigE 4
vMotion 5.0, 5.1, 5.5, 6.0, 6.5, 6.7 10GigE 8

Datastore Limits

Datastore limits apply to migrations with vMotion and with Storage vMotion. A migration with vMotion has a resource cost of 1 against the shared virtual machine's datastore. A migration with Storage vMotion has a resource cost of 1 against the source datastore and 1 against the destination datastore.

Table 2. Datastore Limits and Resource Costs for vMotion and Storage vMotion
Operation ESXi Version Maximum Cost Per Datastore Datastore Resource Cost
vMotion 5.0, 5.1, 5.5, 6.0, 6.5, 6.7 128 1
Storage vMotion 5.0, 5.1, 5.5, 6.0, 6.5, 6.7 128 16

Host Limits

Host limits apply to migrations with vMotion, Storage vMotion, and other provisioning operations such as cloning, deployment, and cold migration. All hosts have a maximum cost per host of 8. For example, on an ESXi 5.0 host, you can perform 2 Storage vMotion operations, or 1 Storage vMotion and 4 vMotion operations.

Table 3. Host Migration Limits and Resource Costs for vMotion, Storage vMotion, and Provisioning Operations
Operation ESXi Version Derived Limit Per Host Host Resource Cost
vMotion 5.0, 5.1, 5.5, 6.0, 6.5, 6.7 8 1
Storage vMotion 5.0, 5.1, 5.5, 6.0, 6.5, 6.7 2 4
vMotion Without Shared Storage 5.1, 5.5, 6.0, 6.5, 6.7 2 4
Other provisioning operations 5.0, 5.1, 5.5, 6.0, 6.5, 6.7 8 1