Data storage vendors continue to roll out support for the latest VMware vStorage APIs in hopes that tighter integration between their arrays and vSphere will improve performance and scalability for customers that make use of the popular virtual server technology.
Below is a cheat sheet on how VMware vStorage APIs can be useful to an IT organization.
Release date: July 2010
What it does/why it's useful: VAAI offloads processing from VMware ESX and ESXi servers to the storage system, preserving resources (including CPU and bandwidth) on the host servers.
"The important thing is that vCenter initiates these requests," said Venu Aravamudan, a senior director of product marketing at VMware. "These are coordinated by intelligence that we have in the virtual infrastructure to be able to drive the storage to do meaningful things, whether you're provisioning virtual machines, taking snapshots of virtual machines, migrating the datastores or whatever."
VAAI currently consists of the following three parts, or primitives:
- Full Copy, also known as Copy Offload: This enables the storage system to make full copies of data within the array, eliminating the need for the ESX Server to read and write the data. Full Copy aims to speed virtual machine (VM) deployment, cloning, snapshots and Storage VMotion.
- Block Zeroing, also known as Write Same/Zero: This enables the storage system to "zero out" a large number of data blocks to expedite the provisioning of new VMs and reduce I/O for common tasks.
- Hardware-Assisted Locking, also known as SCSI Reservation Lock or Offloaded Locking: This allows vCenter to offload SCSI commands from the ESX host server to the storage system so the array can control the locking mechanism while the system does data updates. VMware claims this feature allows 10 times more VMs per datastore.
"SCSI Reservation [Lock] is essentially a command that allows one server to lock stuff while it's doing updates so that nobody else steps on it," said Robert Passmore, a research vice president at Stamford, Conn.-based Gartner Inc. "In a VMware environment, the way they use the SCSI command set in both Fibre Channel and iSCSI can get in the way of other servers doing their work. This feature allows VMware to ask the storage array to control the locking mechanism more precisely than the SCSI command does."
Vendors that support VAAI include Dell Inc. and its Compellent acquisition, EMC Corp., Hewlett-Packard (HP) Co. and its 3PAR acquisition, Hitachi Data Systems, IBM and NetApp Inc.
A fourth VAAI primitive that VMware once disclosed, Thin Provisioning Stun, has yet to emerge. This feature would have allowed vCenter to report an array's thin provisioning state to the ESX Server host so users wouldn't run out of space, according to information on VMware's website. VMware was unable to provide an update on this technology.
Release date: July 2009
What it does/why it's useful: Traditional data protection required backup agents in every virtual machine, sucking processing power from the host server. VADP allows for "agentless backup through the hypervisor by leveraging things like [VMware's] snapshot capabilities in the file system," according to VMware's Aravamudan.
Vendors supporting VADP include CA Inc., CommVault Systems Inc., EMC, HP, IBM, Symantec Corp., Veeam Software Corp. and Quest Software Inc.'s Vizioncore.
Release date: July 2009
What it does/why it's useful: The vStorage API for Multipathing allows vSphere to support advanced data path management software, such as EMC's PowerPath, to improve storage path failover and optimize storage I/O throughput.
"As you deploy virtual machines on vSphere, these partner-based multipathing solutions get plugged in, and you have a lot more redundancy and availability for storage from your virtual machines," Aravamudan said. "And many of the advanced features in those third-party solutions can also still be leveraged through this interface."
Vendors that support VMware's multipathing API include Dell, EMC and HP.