User guide

Technical white paper | HP Enterprise Virtual Array Storage and VMware vSphere 4.x and 5.x configuration best practices
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Table 10 provides the number of drives to use with VAAI.
Table 10. VAAI command controller access
HP EVA Storage
7.2K RPM HDD
10K RPM HDD
15K RPM HDD
EVA4400
*13
65
55
EVA6400
110
60
45
EVA8400
110
60
45
P6300/P6350
140
75
55
P6500/P6550
175
90
65
Best practice for minimum drive requirements for VAAI
• Ensure the HP EVA Storage is configured with an adequate number of drives when using VAAI. Refer to Table 10 for
guidance.
VMware Space Reclamation and EVA
As discussed in the VAAI section above, VMware ESX added support for Space Reclamation in ESXi 5.0. Support of the
UNMAP VAAI primitives enables storage arrays that implement the UNMAP SCSI command to successfully process space
reclamation requests. Starting with firmware 11200000, the HP EVA Storage arrays support capacity reclamation as
support for the UNMAP SCSI primitive has been added. Table 11 shows the HP EVA Storage arrays that support UNMAP.
Table 11. HP EVA Storage arrays supporting UNMAP
HP EVA Storage
EVA4400
EVA6400
EVA8400
P6300/P6350
P6500/P6550
ESX UNMAP support history
Though UNMAP support was added in ESXi 5.0, support for Space Reclamation in ESXi 5.0 was retracted a little while after
ESXi 5.0 released. The performance of UNMAP operations at the storage were directly tied to the success of Virtual
Infrastructure (VI) operations such as, Storage VMotion and VMware VM Snapshots. The longer a storage system took to
process UNMAP commands, the longer such VI operations would take and cause them to effectively timeout. Because of the
disparity in performance observed by various vendors’ storage arrays with respect to the processing of UNMAP commands,
VMware retracted support for Space Reclamation in ESXi 5.0.
ESXi 5.0 patch2 was released soon after ESXi 5.0 and disabled the UNMAP functionality in ESXi. When UNMAP support was
re-introduced in ESXi 5.0U1, ESX UNMAP handling was altered to decouple the space reclamation operation from the
completion of VI operations such as Storage VMotion and VM Snapshots. These operations would no longer automatically
trigger ESX to send UNMAP requests to storage. Instead, a user at their own discretion would have to manually invoke, via
command line, the utility that will reclaim available capacity independently of VI operations.
The newly introduced ESXi 5.5 also requires users to manually reclaim capacity at their discretion by invoking a command
line utility. However, ESXi 5.5 made many significant improvements over ESXi 5.0U1 that are discussed later in this
document.
*
13
EVA4400 only supports a maximum of 96 drives. Hence 7.2K RPM drives can’t meet the minimum number required for adequate VAAI performance.