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Host Deep Dive Stickers and More

Last week we released the VMware vSphere 6.5 Host Resources Deep Dive book and Twitter and Facebook exploded. We’ve seen some pretty bad-ass pictures on our Twitter feeds such as this one by Jamie Girdwood (@creamcookie)

It’s always nice to hear some praise after spending more than 800 hours on something. (When writing and self-publish a book, expect to spend over 90 minutes on one page). Thanks!

The top three most often heard questions were:

  1. When will you release an ebook version?
  2. Do you have any stickers?
  3. When is Niels joining VMware?

When will you release an ebook version?
We hope to get the ebook finalized after VMworld. Vacation time is coming up, and we also need to prep for VMworld (vSphere 6.5 Host Resources Deep Dive: Part 2 [SER1872BU]). It might happen sooner, but that depends on the process of creating an eBook itself. Unfortunately, it’s not as easy as sharing a PDF online. Please stay tuned.

Do you have any stickers?
We got you covered. We met up with our designer over at and explained our wishes. We received a lot of comments on the depth of the book. Such as the one from Duncan’s article Must have book: Host Resources Deep Dive:

As most of you know, I wrote the Clustering Deepdive series together with Frank, which means I kinda knew what to expect in terms of level of depth. Kinda, as this is a whole new level of depth. I don’t think I have ever seen (for example) topics like NUMA or NIC drivers explained at this level of depth. If you ask me, it is fair to say that Frank and Niels redefined the term “deep dive”.

So instead of snorkeling and hovering a bit below sea-level, we help you get into the depths of the material. What better way to express this than a divers helmet. We will bring 250 stickers to VMworld. First come first serve. If you can’t wait, download the 800 DPI PNG here and create one for yourself.

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I think the design rocks, so much that Niels and I decided to put it on some t-shirts as well. We are not backed by a vendor, so we can’t give away shirts. Similar to the book, we kept the price low. We created two campaigns, one for the US and one for EU.This allows you to get the order as fast as possible. The shirts and hoodies come in various colors.

When is Niels joining VMware?
I don’t know, he should though!

Why the Recent Reported Intel HT Bug is Not in Your Data Center

Yesterday I tweeted out the warning message about the HT bug of Skylake and Kaby Lake processors posted on

My tweet got a LOT of retweets. A lot replied with concerns about their systems. I believe most Data Centers will not suffer from this bug as it is present on Skylake and Kaby Lake processors.

What is the Bug?
According to the warning: Unfixed Skylake and Kaby Lake processors could, in some
situations, dangerously misbehave when hyper-threading is enabled.
Disable hyper-threading immediately in BIOS/UEFI to work around the problem. Read this advisory for instructions about an Intel-provided fix.

Unlikely Present in Your Data Center
The reason why I believe most systems in data centers are not hit by this bug is that it solely applies to E3 Xeons from the Skylake microarchitecture. E3 CPUs are designed to operate in a single socket system, they have no QuickPath Interconnect. Therefore unable to create a symmetric multiprocessing system.

The current E5 (dual-socket) system is based on the Broadwell microarchitecture. The Skylake microarchitecture is expected to appear within the next couple of months. According to the report, they will have the fix included when the product launched. If you are running a NUC in your lab, you might want to check to see whether your system might hit that bug

The link will forward you to a perl script that can help detect if your
system is affected or not. Many thanks to Uwe Kleine-König for
suggesting, and writing this script.

Keynoting Deutsche VMUG and London VMUG

Later on this month, I will be attending the Deutsche VMUG and the London VMUG. As part of the events, I have the opportunity to deliver the keynote on the upcoming service VMware Cloud on AWS.

Many of you will already be aware that Niels and I are releasing the VMware vSphere 6.5 Host Resource Deep Dive. Together we will provide a session at both events zooming into ESXi hosts designs, highlighting some interesting behavior from a component and VMkernel perspective.

14 June 2017
KAP Europa, Kongresshaus der Messe Frankfurt
Osloerstrasse 5
Frankfurt am Main, 60327 DE

22 June 2017
10:00 AM – 5:15 PM (UTC)
10 St Bride Street
London, EC4A 4AD

If you can’t make it to the LONDON VMUG, join us at vBeers that night. We will be heading over to the Fourpure brewing company at 22 Bermondsey Trading Estate, Rotherhithe New Road, London

Hope to see you at one of these events!

Memory-Like Storage Means File Systems Must Change – My Take

I’m an avid reader of They always provide great insights into new technology. This week they published the article “Memory-Like Storage Means File Systems Must Change” and as usually full of good stuff. The focus of this article is about the upcoming non-volatile memory technologies that leverage the memory channel to provide incredible amounts of bandwidth to the storage medium. I can’t wait to see this happen and we can start to build systems with performance characteristics that weren’t conceivable a half a decade ago.

The article mentions 3D XPoint and Intel Apache Pass is the codename for 3D XPoint in DIMM format. It could be NVDIMM it could be something else. We don’t know yet. This article argues that storage systems need to change and I fully agree. If you consider the current performance overhead on recently released PCIe NVMe 3D XPoint devices, it is clear that the system and the software have the largest impact on latency. The solved the device characteristics pretty much; it’s now the PCIe bus and the software stack that delays the I/O. Moving to the memory bus makes sense. Less overhead and almost five times the bandwidth. For example, four-lane PCIe 3.0 provides a theoretical bandwidth of close to 4 GB/s while 2400 MHz memory has a peak transfer rate of close to 19 GB/s.

This sounds great and very promising, but I do wonder how will it impact memory operations. The key is to deliver an additional level of memory hierarchy, increasing capacity while abstracting the behavior of the new media.

It’s key to understand that memory is accessed after an L3 miss. It can spend a lot of time waiting on DRAM. A number often heard is that it can spend 19 out of every 20 instruction slots waiting on data from memory. This figure seems accurate as the latency of an instruction inside a CPU register is one ns while memory latency is close to 15 ns. Each core requires memory bandwidth, and this impacts the average memory bandwidth per core. Introducing a media that is magnitudes slower than DRAM can negatively affect the overall system performance. More cycles are wasted on waiting on memory media.

Please remember that not every workload is storage I/O bound. Great system design is not only about making I/O faster; it’s about removing bottlenecks in a balanced matter. It’s essential that the storage I/O should not interrupt DRAM traffic.

An analogy would be a car that can go 65MPH. The car in front of him drives 55 MPH. By selecting another lane, the slower car does not interfere anymore, and he can drive the speed he wants. The problem is in this lane cars typically drive 200 MPHs.

The key point for both NVDIMM as Intel Apache Pass is that adding storage on the memory bus to improve I/O latency should not interfere with DRAM operations.

This content is an excerpt of the upcoming vSphere 6.5 Host Resources Deep Dive book.

Virtually Speaking Podcast: VMware Cloud on AWS & HostDeepDive

Last Friday I had the honor to join Pete Fletcha a.k.a. Pedro Arrow and John Nicholson on their always fantastic podcast Virtually Speaking. Unfortunately, John was ill that morning, but Duncan helped us out by taking a break from his vacation.

We spoke about the upcoming service VMware Cloud on AWS (#VMWonAWS). Why it bring such a tremendous value for customers who are in the process of building a hybrid cloud, and how it can help organizations who are already a customer of both VMware and AWS. Closing off we touched upon the progress of the upcoming book ‘vSphere 6.5 Host Resources Deep Dive‘.

I had a blast being a guest again, enjoy the show!

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