User guide

Technical white paper | HP Enterprise Virtual Array Storage and VMware vSphere 4.x and 5.x configuration best practices

• Plugin-less deployment

The HP EVA Storage firmware 10100000 VAAI implementation is SCSI standards based which is directly compatible with

the standards based implementation of VAAI in ESXi 5. Therefore, no VAAI software plugin is required when using ESXi 5

with HP EVA Storage VAAI enabled.

In this paper we will not explain what each primitive does because that subject has been abundantly discussed in other HP

EVA Storage documentation such as the HP EVA Storage array release notes. On the other hand, the paper will focus the

discussion on important caveats to take into considerations when deploying VAAI with HP EVA Storage while highlighting

recommended VAAI deployment best practices

VAAI alignment considerations

Starting with ESXi 5, VMware VMFS partitions created with ESXi 5 are aligned on 1MB boundary of the underlying logical unit

address space presented from storage. Therefore, all VMDKs carved from VMFS volumes are also aligned on 1MB

boundaries.

On the other hand, on ESX 4.1, VMFS partitions are 64KiB aligned and VMDKs carved from these VMFS volumes in turn are

64KiB aligned. When an ESX/ESXi 4.1 host is upgraded to ESXi 5, datastores that were created under ESX/ESXi 4.1 will retain

the alignment they were created with.

Because VAAI WRITE SAME and XCOPY operations are performed respectively to initialize or clone VMDKs, these operations

conform to the alignment of the VMFS partition address space. When deploying HP EVA Storage VAAI solutions, VMFS

partitions to be used for VAAI acceleration must be 64KiB or 1MB aligned.

Datastore that are not 64KiB or 1MB aligned will not be able to leverage VAAI acceleration benefits and will revert back to

using legacy ESX data movers to perform clone and zeroing operations. For this reason, when planning to deploy VAAI with

HP EVA Storage, datastores that do not meet this alignment recommendation need to be re-aligned to 64KiB or 1MB

alignment. In some cases this may require evicting all the VMs from this datastore, then deleting and recreating the

datastore with the desired alignment.

Best practice for aligning VMFS volume for use with HP EVA Storage VAAI

• VMFS datastore must be aligned to either 64KIB or 1MB boundary for use with HP EVA Storage VAAI integration.

VAAI transfer size consideration

VAAI WRITE SAME requests on ESX 4.1 and ESXi 5.x have a default transfer size of 1MB whereas XCOPY requests default to

a 4MB transfer size (tunable to as much as 16MB). For maximum performance of VAAI offloading operations to storage, the

HP EVA Storage has been optimized for XCOPY and WRITE SAME request that are multiples of 1MB. Transfer sizes that are

non-multiple of 1MB, will revert to utilizing ESX legacy data movers. Furthermore, note that VMware VAAI does not support

clone operations between datastores of different block sizes. So when using ESX 4.1 with EVA, it is important to ensure that

the datastores that are used for VAAI clone operations are either 64k or 1MB aligned and that they are also of the same

block size.

VAAI and EVA proxy operations considerations

As discussed earlier in this paper, HP EVA Storage arrays are asymmetric active-active arrays and ALUA compliant. In this

architecture, a logical unit can be accessed through both controllers of the EVA. However, one of the two controllers is an

optimal (often referred to as preferred) path to the logical unit. VAAI WRITE SAME and XCOPY primitives will adhere to these

controller preference rules as follows:

• WRITE SAME commands to a logical unit will be sent to the controller that is the optimal path to the logical unit.

• XCOPY commands copy data from one logical unit to another (where source and destination are allowed to be the same).

During XCOPY operations, XCOPY commands are sent to the controller that owns the destination logical unit.