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Top 5 Planet V12n blog posts week 14

It seems that podcasts are getting more popular by the day. I usually don't add them to the top 5 as it's not really a blog post however some of them would deserve it. A couple of weeks I already mentioned Mike Laverick's chin wags and this week I want to give an honourable mention to Virtumania hosted by Rich Brambley and Marc Farley. 

  • Joshua Townsend – Storage Basics – Part VI: Storage Workload Characterization
    You’ll recall that we divide into 1000 to remove milliseconds from the equation, leaving (Seek Latency + Rotational Latency) as the important part of the equation. Rotational latency is based on the spindle speed of the disk – 7.2k, 10k, or 15k RPM for standard server or SAN disks. If we consider the same Seagate Cheetah 15k drive from Part II, we see that rotational latency is 2.0ms. The only way to change rotational latency is to buy faster (or slower) disks. This essentially leaves seek latency as the only variable that we can “adjust”. You’ll also recall that seek latency was the larger of the latencies (3.4ms for read seeks, and 3.9ms for write seeks) and counts more against IOPS capability than does rotational latency. Seeking is the most expensive operation in terms of performance.
  • Rich Brambley – Why Does Cloning A VM From Template Take A Long Time?
    Obviously, the type/performance of the disks, the number of disks, and the type of array makes a huge difference. I should also point out that I am using 8 ms as the value for the seek latency. I’m not as focused on technical accuracy because my point is served without it, but changing this value makes a significant difference as well. If you want technical accuracy and more explanation about some of the numbers to use in the calculator check out these posts on the topic of IOPS and the impact on a virtual environment…
  • Luc Dekens – LUN report – datastore, RDM and node visibility
    When you are running multi-node vSphere clusters, you probably already had the experience that one or more of your LUNs were not visible on all nodes. Now you can try to find out which LUN is missing on which node the hard way through the vSphere client. Or you can use the force of PowerCLI and run a script that will report all this in a handy spreadsheet.
  • Scott Drummonds – Processor Utilization Calculations
    Where things get really confusing is when these results are combined into three system-wide, aggregate utilization numbers, as seen by esxtop’s batch printout. The three utilization types above generated different utilization numbers. Unfortunately esxtop’s batch mode labels these counters slightly differently.
  • Vaughn Stewart – Raising Awareness Around the Misalignment of Data
    Duncan Epping – Aligning your VMs virtual hard disks
    In my opinion there is no need to discuss VMFS alignment. Everyone, and if  you don’t you should!, creates their VMFS via vCenter which means it is automatically aligned and you won’t need to worry about it. However you will need to worry about the Guest OS. Take Windows 2003, by default when you install the OS your partition is misaligned. (Both Windows 7 and Windows 2008 create aligned partitions by the way.) Even when you create a new partition it will be misaligned. As you can clearly see in the diagram above every cluster will span multiple chunks. Well actually it depends
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Duncan Epping

About Duncan Epping

Duncan Epping is Principal Architect at VMware (R&D, Integration Engineering) and is focused on vCloud / vSphere architecture and integration. He was among the first VMware certified design experts (VCDX 007). He is the co-author of several books, including best seller vSphere 5.1 Clustering Technical Deepdive. He is the owner and main author of the leading virtualization blog yellow-bricks.com.