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Category Archives: Performance

Effect of VAAI on cloning with All Flash Arrays:

Cloning virtual machines is an area where VAAI can provide many advantages. Flash storage arrays provide excellent IO performance. We wanted to see what difference VAAI makes in virtual machine cloning operations for “All Flash Arrays”.

For the test 500GB of random data on a VMDK was created on a Linux virtual machine. This virtual machine was then cloned with VAAI turned off and then on to study its impact. The results of the testing truly attest to the big benefits that VAAI bring to massive write operations.

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Flash to the Rescue, Virtualizing Business Critical Applications in a Flash

There is no doubt that the barriers to virtualization have been rapidly falling. In fact today with VMware’s Monster VM capabilities and the scalability of vSphere 5.5, many organizations have recognized that practically any application can be virtualized and they have adopted a virtualization first policy. But there are still some customers that have been hesitant about virtualizing their most critical applications.  Often times I/O bottlenecks and high storage latency are the cause for poor application performance.  That is where a new breed of storage comes to the rescue.

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Benchmarks – Keeping Perspective

As a performance guy, my world is full of benchmarks – both good and bad.  I wanted to share my perspective of them, as they often seem to make people crazy.

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PVSCSI and Large IO’s

Here’s a behavior that a few people have questioned me about recently:

Why is PVSCSI splitting my large guest operating system IO’s into smaller blocks?

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What is PreferHT and When To Use It

I’ve been involved recently in a couple situations in which the ‘preferHT’ advanced setting has been implemented, but for the wrong reasons. I want to re-clarify how and when it should be used. As with many advanced settings, it can be helpful or hurtful.

The Myth

“PreferHT exposes Hyper-Threading to the guest operating system” – False!

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Updated VMware Mobile Knowledge Portal

The VMware Mobile Knowledge Portal iOS and Android app has recently been updated. It sports a great new look and feel and makes finding the information you need even easier by grouping it by area in our SDDC vision.

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When to Overcommit vCPU:pCPU for Monster VMs

VMware’s conservative guidance about overcommitting your pCPU:vCPU ratio for Monster virtual machines is simple – don’t do it.

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Which vSCSI controller should I choose for performance?

I wrote a blog article in Oct 2010 on this same topic that is still frequently referenced today so I figure it was due for an update.

So what should I choose as my vSCSI controller and what are the differences between them? Continue reading

BIOS Power Policies Affect Performance

How should one set the BIOS power management policies of their VMware infrastructure for maximum virtual performance?

Simple: OS Controlled in the host BIOS, Balanced within vSphere

But are there exceptions?

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Microsoft Operating System Time Sources and Virtual Hardware 10

More recent versions of Microsoft operating systems contain the ability to detect if they are running virtualized or not.  This is accomplished through the checking of a CPUID hypervisor-present bit presented by the VMware virtual hardware.  Since virtual hardware 7, VMware has implemented this interface, which is required by the Microsoft SVVP program.

FACT: Did you know VMware ESX 3.5u2 was the world’s first hypervisor to be qualified under the Microsoft SVVP program?

However, as Microsoft continues to change and update its specifications, lets look at a specific behavior in which virtual machine performance can be impacted by the operating system accessing a time source inefficiently. Continue reading