Wednesday, 9 December 2015

VMware vSphere Storage APIs – Array Integration (VAAI)

What is VAAI?


  • VAAI is a set of VMware vStorage API and SCSI commands designed to provide and efficient communication between ESXi hosts and storage arrays which implements specific T10 storage standards.
  • The APIs define a set of “storage primitives” that enable the ESXi host to offload certain storage operations to the array.
  • It reduces resource overhead on the ESXi hosts and can significantly improve performance for storage-intensive operations such as storage cloning, zeroing. 
  • The goal of VAAI is to help storage vendors provide hardware assistance to speed up VMware I/O operations that are more efficiently accomplished in the storage hardware.
  • Without the use of VAAI, cloning or migration of virtual machines by the vSphere VMkernel Data Mover involves software data movement
  • The Data Mover issues I/O to read and write blocks to and from the source and destination datastore. 
  • With VAAI, the Data Mover can use the API primitives to offload operations to the array if possible.
  • VAAI provides  Atomic Test & Set (ATS) during creation and locking of files on the VMFS volume.
  • VAAI Provides Clone Blocks/Full Copy/XCOPY, which is used to copy or migrate data within the same physical array.
  • Operations Like ATS/Clone Blocks/Full Copy/XCOPY can be controlled with the help of advanced parameters like HardwareAcceleratedLocking, HardwareAcceleratedMove.



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