Volume host affinity based VM placement

Cinder scheduler schedules volume creation on certain host based on scheduler filters in case of multi-node setup. For local volume backends like LVM, the volume resides locally on the host where volume create was scheduled.

For clustered filesystems like IBM General Parallel File System (GPFS) which provides features like FPO (File Placement Optimizer), the volume create command will be run on that host and volume will be created locally if FPO is enabled. (FPO ensures that the node writing data directs the write to its own node for the first copy, and to the disks in other nodes for the second and third copy (if specified). This ensures that the entire file resides on local disks of one node. FPO is designed for efficiency in case of Hadoop and MapReduce workloads. IBM GPFS Volume Driver can be used to configure backends that use FPO enabled GPFS storage pools. It also supports file level FPO configuration using which one can ensure that the cinder volume being created resides completely on one node and is not striped across multiple nodes of GPFS cluster.)

There can be various use cases that leverage the volume locality information, irrespective of cinder backend being used, and instantiate the VM closer to where the volume resides.