VSAN Design Consideration: Booting ESXi from USB with VSAN?

One thing most probably won’t realize is that there is a design consideration with VSAN when it comes to installing ESXi. Many of you have probably been installing ESXi on USB or SD and this is also still supported with VSAN. There is one caveat however and this caveat is around the total number of GBs of memory in a host. The design consideration is fairly straight forward and also documented in the VSAN Design and Sizing Guide. Just to make it a bit easier to find it I copied/pasted it here for your convenience:

  • Use SD, USB, or hard disk devices as the installation media whenever ESXi hosts are configured with as much as 512GB memory. Minimum size for USB/SD card is 4GB, recommended 8GB.
  • Use a separate magnetic disk or solid-state disk as the installation device whenever ESXi hosts are configured with more than 512GB memory.

You may wonder what the reason is, the reason for this is that VSAN will use the core dump partition to store VSAN traces that can be used by VMware Global Support Services and the VMware Engineering team for root cause analysis when needed. So make sure when configuring host to keep this in mind when going above 512GB of memory.

Please note that this is what has been tested by VMware and will be supported, so this is not just any recommendation but could have impact on support!

Virtual SAN GA update: Flash vs Magnetic Disk ratio

With the announcement of Virtual SAN 1.0 a change in recommended practice when it comes to SSD to Magnetic Disk capacity ratio was also introduced (page 7) has been introduced. (If you had not spotted it yet, the Design and Sizing Guide for VSAN was updated!) The rule was straight forward: Recommended SSD to Magnetic Disk capacity ratio is 1:10. This recommendation has been changed to the following:

The general recommendation for sizing flash capacity for Virtual SAN is to use 10 percent of the anticipated consumed storage capacity before the number of failures to tolerate is considered.

Lets give an example to show the differences:

  • 100 virtual machines
  • Average size: 50GB
  • Projected VM disk utilization: 50%
  • Average memory: 5GB
  • Failures to tolerate = 1

Now this results in the following from a disk capacity perspective:

100 VMs * 50GB * 2 = 10.000GB
100 VMs * 5GB swap space * 2 = 1000GB
(We multiplied by two because FTT was set to 1)

This means we will need 11TB to run all virtual machines. As explained in an earlier post I prefer to add additional capacity for slack space (snapshots etc) and meta data overhead, so I suggest to add 10% at a minimum.This results in ~12TB of total capacity.

From an SSD point of view this results in:

  • Old rule of thumb: 10% of 12TB = 1.2TB of cache. Assuming 4 hosts, this is 300GB of SSD per host.
  • New rule of thumb: 10% of ((50% of (100 * 50GB)) + 100 * 5GB) = 300GB. Assuming 4 hosts this is 75GB per host.

Now lets dig some deeper, 70% read cache and 30% write buffer. On a per host basis that means:

  • Old rule: 210GB Read Cache, 90GB Write Buffer
  • New rule: 52,5GB Read Cache, 22,5GB Write Buffer

Sure from a budgetary perspective this is great, only 75GB versus 300GB per host. Personally, I would prefer to spend more money and make sure you have a larger read cache and write buffer… Nevertheless, with this new recommendation you have the option to go lower without violating any of the recommendations.

Note, this is my opinion and doesn’t reflect VMware’s statement. Read the Design and Sizing Guide for more specifics around VSAN sizing.

VMware Virtual SAN launch and book pre-announcement!

Today is the day, finally… the Virtual SAN (VSAN) launch. Many people have been waiting for this one. With 12.000 plus beta participants this was one of the biggest projects I have ever seen within VMware. It is truly impressive to see how the product has grown and what the team has done. Before I will provide you with some of the details of the announcement I want to share something else that all of you should look out for:

Cormac Hogan and I decided it was time for a book on Virtual SAN. Both of us have published many articles about VSAN the last 9 months and have been working with the product for over a year now so it only made sense. We have decided, and this wasn’t an easy decision for me, to go with VMware Press. When I say “not an easy decision” I don’t want to sound negative about using publisher, but it is just that I have had a great experience (and results) with self-publishing. It was time for a new experience though, try something different. As we speak we are working hard to get the final set of chapters in for review / editing and we are hoping to have the book available before VMworld. I am guessing that the rough cuts will be available through Safari in the upcoming weeks, if so I will let you know via a blog post.

Now lets get back to the topic of the day again, Virtual SAN Launch… So what was announced today?

  • General Availability of Virtual SAN 1.0 the week of the 10th of March
  • vSphere 5.5 Update 1 will support VSAN GA
  • Support for 32 hosts in a Virtual SAN cluster
  • Support for 3200 VMs in a Virtual SAN cluster
  • Full support for VMware Horizon / View
  • Elastic and Linear Scalability for both capacity and performance
  • VSAN is not a VSA. Performance is much better than any VSA!
  • 2 Million IOPS validated in a 32 host Virtual SAN cluster
  • ~ 4.5PB in a 32 host cluster
  • 13 different VSAN Ready Node configurations between Cisco IBM Fujitsu and Dell available at GA, more coming soon!

Once again, great work by the VSAN team. Version 1.0 just got release, and I can barely wait for the next release to become available!

As he faced the sun he cast no shadow

Those who are wondering, the title is a quote from one of my favourite Oasis songs. This phrase to me talks about someone who goes through life unnoticed. This phrase is what I thought of when thinking about orphans and orphanages. I felt that the majority of them would go unnoticed, would have no opportunity, would not receive the love and/or affection they need. Reality unfortunately is that this is true in many cases.

While flying back from Vietnam, I took some time to think about my experience working with Orphan Impact and Team4Tech on behalf of the VMware Foundation. I guess it is fair to say that I did not expect what an impact something like providing computer classes can have on these orphans. As I mentioned in my previous blog post: Love / affection, appreciation, acknowledgement, a chance… this is what truly matters. This is ultimately what these kids get from the awesome team from Orphan Impact, yes they provide computer classes but the social aspects are far more important if you ask me.

Someone once said that helping out in these orphanages was short term thinking, would not make a difference in the long run, that the government has to change and give more to the unfortunate. Maybe he was right, at least to the point where the government should invest more. I don’t think however we should wait for that to happen by itself, it only happens when you raise awareness of the situation. Don’t get me wrong, I don’t think we changed the world by going on a 12 day trip to Vietnam. However, if these 12 days gave only one of those kids in the 4 orphanages we visited the feeling he or she matters ,and therefor has a better chance of surviving, than it was more than worth it!

In the end, we can not control someones journey, but we can do your best to help them navigate and give them the confidence needed to determine which direction they take.

Thanks VMware, Team4Tech and Orphan Impact for allowing me to be part of this great and eye opening experience.

Startup News Flash part 14

Part 13 of the Startup News Flash… Hopefully not an unlucky one for the startups featured. Just a short one considering I am in Vietnam and away ‘from work’ for the last 2 weeks.

A3Cube is a startup which came out of stealth recently and announced as they call it a ‘brain inspired’ data plane encapsulated in a NIC designed to bridge supercomputing benefits to the enterprise. The core of their solution is called Ronnie Express. They aim is to eliminate the I/O performance gap between CPU power and data access performance for HPC, Big Data and data center applications. A3CUBE’s In-Memory Network technology allows direct shared non-coherent global memory across the entire network, enabling global communication based on shared memory segments and direct load/store operations between the nodes. Basically a server “interconnect” solutions for lrge scale. They took the word “scale” serious by the way and can go up to 64,000 nodes. For more details, I highly recommend to read this excellent article by Enrico.

Infinio just announced Infinio Accelerator 1.2. This new version of the Infinio Accelerator now supports vSphere 5.5. Useful to know for those who have a home lab, Infinio is running a limited-time offer of free non-expiring licenses for test labs. Hit their website to find out more.