VMware vSphere® Storage APIs – Array Integration (VAAI), also known as hardware acceleration or hardware offload APIs, are a set of APIs enabling interaction between VMware vSphere ESXi™ hosts and storage devices. The APIs in VAAI are supported by a block or NAS array (e.g. storage system) and can offload different functions from the vSphere hypervisor and virtual machine (VM).VAAI has been established to handle issues industry faces while trying to expand Virtual Machines mainly during sizing storage, rapid VM provisioning and maintaining application performance. It has the ability offload specific storage operations to compliant storage hardware, which results in less CPU, memory and storage fabric bandwidth consumption. In other words, VAAI removes blocks, and offloads tasks that are “expensive” and place a heavy load on ESX resources to storage arrays. This enables improved performance, scale and efficiency to a very large extend
VAAI can be used in the following functions:
- Atomic Test and Set (ATS)
- Full Copy / XCOPY / Clone Blocks
- Data Deduplication and Full Copy
- Block Zeroing / Write Same / Zero Blocks
- Block Delete / Unmap
- Thin Provisioning Stun / TP Stun
- The below table summarizes the impact of VAAI and deduplication on a clone operation for a VM of size 10GB
Source: Qadstor
|
Source LUN
|
Destination LUN
|
Remarks
|
|
|
Without VAAI
|
10 GB read
|
10 GB written
|
Utilizes both network and server
resources |
|
With VAAI (no dedupe/post-process
dedupe) |
10 GB read
|
10 GB written
|
Network and server resources
minimal. Array resources used for read and write operations |
|
With VAAI (Inline dedupe)
|
10 GB read
|
0 GB written
|
Network and server resources
minimal. Array resources spent in reads and deduplication |
|
With VAAI (QUADStor)
|
0 GB read
|
0 GB written
|
Network and server resources
minimal. Array resources spent only in deduplication |
To conclude, the main advantage of VAAI is definitely excellent performance followed by facts like enabling VMware and it’s hypervisor to scale out.The VMware community is on a spree of continuous improvement of the APIs with its every release. Many more API integrations, snapshot offload and array management can be expected in the near future.
