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OK, so I've calculated the results, and the response is overwhelming!  There is absolutely an interest in the second annual VMworld Europe photowalk, so I am absolutely organizing it!

What: 2nd Annual VMworld Europe Copenhagen Photowalk
When: Monday, October 17th - 12:30PM CEST
Where: Nyhavn, Copenhagen, Denmark (See Starting Point Map)
Who: Anyone of any skill level.  iPhones to Pro Gear.  Anyone interested in sharing knowledge, seeing the city, and taking photos

If interested in attending, please send me an email to: This e-mail address is being protected from spambots. You need JavaScript enabled to view it. or mention me on twitter @VMGuru.

Key Sites

• Nyhavn
• Amalienborg Palace
• Kastellet
• The Little Mermaid Statue
• Rosenborg Palace Garden
• Marble Church

Starting Point - Nyhaven, Copenhagen, Denmark

The Route

Route Map External Link

I was sketching out some diagrams today and started to think about how the time frame that we analyze and how it relates to Capacity Management.  The concept of "Working" or "Business" hours actually plays a vital role in how capacity is accounted for and accommodated in the datacenter.

I often relate introducing business hours into capacity management to being a decision point during a breakup.  There is a line that is drawn between "Lets remain friends" and "Never call me again".  With business hours, we need to determine how big of a window we want to consider for the data we care about.  This is going to be different for every organization out there.  For the purpose of simplicity, let's look at a window in which I only care about data between 6am and 6pm.

It appears that when I did my site re-design a while back, I left out a few key blog posts.  I was kindly reminded today, that my CBT Tracker post no longer exists, so I've decided to bring it back from the dead, as I was under the impression many people found high value in understanding data growth patterns of individual VMs in their environment.

I took it as a personal challenge this week to leverage PowerShell, PowerCLI and the vSphere API to track the amount of data that changes in a VM over a regular interval window. It turns out VMware does make it quite simple to query what blocks in a VMDK file have changed and what the length of data is as long as you know how to structure the API call.

Attachments:

CBT_Tracker.ps1.zip

[Zip File containing the CBT Tracker script PS1 File]

2 Kb

VMware Paravirtualized SCSI (PVSCSI) introduced in vSphere was a special purposed driver for high-performance storage adapters that offered greater throughput and lower CPU utilization for virtual machines. According to tests PVSCSI offers 12% improvement in throughput and 18% less CPU cost compared to LSI SCSI.

In the early releases it had lots of limitations:

• FT not supported
• PVSCSI on boot disk not supported
• Hot Add not supported
• Only suited for heavy disk IO demanding workloads due to how PVSCSI handles interrupt coalescing
• Very limited OS support
• Not for Direct Attached Storage

All of these limitations are gone now (vSphere 4.1) except the two last bullets.

Lots of benefits:

• Simplicity, only having one template to maintain
• Don´t have to worry about changing virtual hw/driver if VM is starting to require higher disk IO at a later state
• Allows you to run more VMs -> higher VM density
• Increased disk IO performance

I wouldn´t change to PVSCSI on existing VMs if there is not a demand for high disk IO. But I would like to see more adoption of PVSCSI going forward as most people are basing their decisions on old and inaccurate information.

Please leave some comments on your experiences on PVSCSI (good and bad).

For more info:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1017652

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1010398

http://www.vmware.com/pdf/vsp_4_pvscsi_perf.pdf

/Mattias