Determine your vSphere storage needs – Part2: Performance

Besides capacity, performance is probably one of the most important design factors.

  • IOPS
  • Latency

The first step is to determine your performance needs in IOPS. This is probably the hardest part. In order to determine your IOPS needs, you have to know what type of virtual machines or applications, and there corresponding I/O characteristics your going to run on your storage solution.

You can take 2 approaches to determine this:

  • Theoretically
  • Practical

In the theoretical approach categorize the type of virtual machines you’re going host on your storage solution. For example:

  • Database
  • Email
  • Windows
  • Linux
  • Etc

Then you determine the corresponding block size, read/write ratio, and if it’s sequential or non sequential data per type.

In the practical, or real live method, we’re going to use a tool to determine the type of IO issues by your current virtual machines. There are a couple of tools available for this. One of them is PernixData Architect. This tool gives in depth information about your storage IO workload  including read/write ratio and which block size is used.

Of course you can use vCenter to see your current read/write ratio, but not the block size which is used. You even can use ESXTOP in combination with perfmon to determine your IO workloads. The last option isn’t the most easiest way, but it’s a option if you don’t have a vCenter or budget for Architect.

You can make a table like this.

Type #VMs Blocksize #KB Avg. #IOPS %READ %WRITE Sequential Note
Windows 2000 4 50 60 40 No Basic application servers
Linux 1000 4 50 60 40 No Basic application servers
MS SQL 4 64 1000 65 35 No 2 for production, 2 for DevOPS

Note: Values are only a example. Your environment can (and probably will be) different.

So, why want you to determine the read/write ratio and block size?

Every storage solution has his own way of writing data to the disks. The performance depends on the block size, read/write ratio and RAID-level (if any) used. A Windows virtual machine can use a block size of 64k. When a storage solutions write data in 4k block. 1 IO from this virtual machine will issue 16 IO’s on the storage. If your storage solution uses RAID6, you have a write penalty of 6. Ok, so in this example. When a windows guest issues 1 64k IO, this results in (16*6) 96 IO’s on your storage. Hmmm, kind of make you think not?

Nowadays, every storage system had some type of cache onboard. This makes it hard to determine how many IOPS a storage system can deliver. But remember, a write IO can be handled by the cache. But a read IO, which is not already in cache, needs to be read from disk first.

Second, you have to determine the average latency you want to encounter on your storage solution. Every storage vendor will promote his solution as a low latency storage. This depends on where you measure this latency.

Below a overview where latency is introduced in a SAN or NAS solution.

Storage Latency

As you can see, there are 12 places where latency is added. Of course, you want the lowest latency in the virtual machines. As this hard to determine, if you have 5000+ virtual machines, the next best place is the VMkernel.

Again, there a several tools to determine the read and write latency in the VMkernel. ESXTOP, vCenter of tools like Architect are great examples.

In my opinion these are the maximum average latency you want to encounter.

Type Read Write
VMs for servers  2ms  5ms
VMs for desktops or RDS <1ms <2ms

As always, lower is always better.

So, how do you determine which is the best storage solution for your needs?

Talk to your storage vendor. Give the table you’ve created and ask them which type and model suites your needs, and how to configure the storage solution. This way, your sure that your getting the right storage for your needs. And if, in the future, you’re encountering storage problems, you can check if the storage solution is performing according the requirement you discussed with your storage vendor.


New Community reward: Nutanix NTC

Yesterday Angelo Luciani @AngeloLuciani announced the 2016 Nutanix Tech Champions (#NutanixNTC), and I’m please to say that: “I made it”. The list has grown since 2015. But that’s was expected as Nutanix continues there success story with the #Acropolis Hypervisor and #Webscale solution.

For you who don’t know what Nutanix NTC stands for a quote:

This program recognizes Nutanix and web-scale experts for their ongoing and consistent contributions to the community and industry. It also provides them with unique opportunities to further expand their knowledge, amplify their brand, help shape the future of web-scale IT.

A complete list of all Nutnix NTCs 2016 can be found Nutanix NTC 2016.

Last October I was delighted achieving my #VMware #VCDX. Maybe 2016 will bring Nutanix #NPX?


My VCDX journey

Friday 30 October 2015, 9:30 in the morning. I’m in the middle of a lesson talking about SRM and recovery plans, I see a popup on the top right of my screen: “VCDX Defense Results”.
Me to my students: “Sorry, this is not what I normally do. But I have to check this email”.

Michael Wilmsen,

Congratulations! You passed! It gives me great pleasure to welcome you to the VMware Certified Design Expert community.

Your VCDX number is 210.

My journey started about 1 year ago. I was contracted by a program for a city in the Netherlands to architect a 3800 Horizon View Solution. I already passed the VCAP DCD and DCA exams, so this was my opportunity to go for VCDX.
After 6 months, the technical design document was at version 1.0 and the implementation started. At this time I really didn’t had the time to go for VCDX. After 4 months the project was at his end and the VCDX was back on my mind. But how to go from here?
First I asked permission from the customer if I could use the design for my VCDX defense. This was no problem as long as I anonymize the design. Ok, no problem of course. My design was in Dutch, so I had to translate it anyway.
In June I attendant Nutanix .NEXT (my design was based on Nutanix hardware). There I had a conversation with @repping. Nutanix was willing to help me out with a mentor and they arrange @vcdx026 Alexander Thoma for me. Alexander is also know as the Iron Panelist has he did more than 100+ panels when he worked for VMware. Now that he works for Nutanix he can mentor me, but is still restricted by the code of conduct.
After I came back from Miami I looked at the defense dates for 2015. These where in October but the application had to be submitted before 25 of august. This gave me about 3 months but my holiday with the family was about 3 weeks in august. This limited my time.
At this point I said to myself: “Either you go for it, or you probably won’t to it again for the next few years.”.
I had a good conversation with my wife because this is going to take a lot of free time and late working. You probably heard this before, this is really important! If you don’t have the support from your family, and you don’t want a divorce, don’t start. I’m lucky enough to have a great wife who supports me al the way, although this isn’t always easy for her.
Just before my holiday I had a concept version the design ready. My collogue and friend Joop Kramp offered me to do a review. In my final week of my family holiday he provided me the necessary feedback. As I wanted to know what his feedback was, my wife agreed that I could spend a morning in Italy going to his comments.

Screen Shot 2015-11-04 at 20.49.31
When I was back home, I spend the last to day’s before sending my application to VMware finalizing my documents. On the 25 of august 2015 at 4PM I clicked the send button.
At this point I was more relaxed. This ended a few weeks before the defense date. These weeks friends and family often asked where I was with my mind. Easy, going over and over my design. Thinking about possible question I could get.
My defense date was on the 22 of oktober in Stains-upon-thames, UK. My wife wanted to go to London for a couple of years to go to the Phantom of the Opera. So I looked at possible flights and dates for the Phantom. The only possible option for the Phantom was the night before my defense. This made me a little nervous. Didn’t I have to go over my design one more time the night before. But when I thought it over, I said to myself: “Your defense doesn’t depends on 1 evening the night before. If that’s the case, you are not ready to defend.”
So I went to the Phantom of the Opera with my wife and really enjoyed it. The next morning we drove to Stains.
At 2PM my defense started. I thought I would be nervous, but this wasn’t the case. Actually, I was really relaxed. Looking forward to the defense.
The defense part I really enjoyed. This was more a conversation between equally minded people. Although I was stated that you don’t know how the panel thinks about your answer, I felt they understood me. In my case I had some weird assumptions as the where political. For this I had good answer why this was.
The design and troubleshooting part was more frustrating. You’re constantly thinking: “Am I not forgetting something?”
After the defense was over my wife asked me how it went? My response: “Ok, I think. But I really don’t know if its enough. Did I give the correct in-depth answers the panel was looking for?”
The rest you know. I’m VCDX number 210!

Do I have some tips that you haven’t found already Googling the internet? There is one thing I can think of.
If you’re allowed to defend, your design is technically approved. The defense part is about knowing your design and that you can defend yourself. This is not about knowing how for example Host Isolation Response works. You have to explain why you made the decisions to go for Power Off. In other words, you’re not tested about your technical knowledge. You have already proven this by passing your VCAP exams and being allowed to defend.

Of course I want to thank a few people
First of all, my wife, Marjolein. Again. Thanks honey! You made this possible for me!
Alexander Thoma, The Iron Panelist! Thanks for our late night Webex discussions and clear DMs when I asked you a question. They where sort and clear. Just the way I like them.
Niels Hagoort (VCDX212), Rutger Koster (VCDX209) and Leo Scheltema. My VCDX study buddy’s. We had some good discussions and a nice mock exam in my pub.
Raymon Epping. Thanks for your support and that of Nutanix by providing me feedback and a mentor.
Michael Webster (VCDX066). Thanks for the mock exam. Although you couldn’t give me feedback if I did ok, it helped me out allot how a defense goes.
Duncan Epping (VCDX007) and Frank Denneman (VCDX029). You guy’s made me believe that I was able to go for VCDX. This was the real first step for me. Frank, Thanks for the tips so I was more relaxed the day’s before my defense.

A few day’s ago I read a tweet asking: “I’ve I want to go for VCDX, what is the first step?”. My response: “This tweet is your first step.”.
If you want to go for VCDX, go! It’s better failing in trying than not to try at all.
And if you need a mentor, you can contact me.


Determine your vSphere storage needs – Part 1: Capacity

Currently I’m working on a project where I have been asked to determine the storage requirements for a new storage solution. The customer is going to run a VMware vSphere 6 environment in a active-passive twin datacenter setup.

As I was gathering the customer requirements I thought to write a blog post how this process goes will I’m working on it.

When designing a vSphere storage setup you have to design the following sections.

  1. Capacity
  2. Performance
  3. Availability
  4. Security
  5. Connectivity

Let’s start with the first one, capacity.

Capacity is the easiest part of the design and with most storage solutions it’s easy to extend. You can use the following formula to determine your total RAW capacity storage need:

((TotalVMs * (OSDriveCapacityGB + AvgMemSizeVMNotReserved)) + TotalDataGB) * (RestoreCapacity% + SnapshotReserveCapacity%) = TotalGB

For example:

  • You have 1000 VMs.
  • Every VM has a C-Drive (or root) of 50GB.
  • The average memory size of a VM is 8 GB where nothing of is reserved.
  • You want to reserve 10% for backup restores.
  • You want to reserve 5% for snapshots.
  • Total data capacity is 50TB


This makes:

((1000 * (50GB + 8GB)) + 50TB) * (10% + 5%) = 88,14 TB

This is the RAW capacity available to the VMware vSphere hosts, and doesn’t take RAID overhead, and storage features like thin provisioning, deduplication and compression into account. These storage features are most of the time reasons for a discussion whether if you want to use these features and what the impact on the performance is.

Using features like compression and deduplication depend on the use case.

I can imaging that you want to use compression and deduplication for archiving purposes, and not for production virtual machine like MS SQL or SAP because of the potential performance impact.

The type of RAID level used by the storage solution implicates the RAID overhead and how you size the storage solution. Do you configure 1 large container containing all disks? Or do you create multiple containers? This again depends on the type of storage solution, and the capacity and performance requirements you have. The performance part I will cover in a later blog post. For now we focus on the storage capacity.

VMware has 3 type of VMDKs.

  • Thin
  • Thick (Lazy)
  • Eager Zero Thick

I’m not going to explain in-depth the VMDK type because this I well covered in Death to false myths: The type of virtual disk used determines your performance, Thin or thick disks? – it’s about management not performance, and http://www.vmware.com/pdf/vsp_4_thinprov_perf.pdf blog post.

If you’re going to use thin provisioned VMDKs in you environment you can subtract the free space from your RAW capacity needs. Do take into account that thin VMDKs will grow and you have to monitor the free capacity of your storage solution to make sure that it won’t fill-up. This will result in virtual machines who will be unavailable.

So how your (new) storage solution is going to provide your RAW capacity depends on the type of storage solution. In my opinion you have to talk with your storage vendor what is the best configuration based on your company needs.

What you do need to take into account is how easy it is to extend the capacity of your storage solution. The new storage solution probably will run for the next 5 years. No way that you can determine the capacity need for the next 5 years. And when you have to add capacity, do you have to reconfigure storage pools, LUNs and/or RAID groups? Can this be done on the fly without impacting production workloads?

Of course performance definitely will impact the setup and configuration of your storage solution. This I will cover in a later blog post.


Silicon Valley Road Trip – Day 2

Today we had the pleasure to visit to other companies in Sillicon Valley, Nutanix and Pernixdata. Although these 2 companies cannot called an startup anymore they had quite some interesting stuff to show us.

At Nutanix we had a 1 hour meeting with @stevenpoitrais (who wrote the Nutanix Bible). If you ever worked with Nutanix you probably visits his web page. If not, you should!

Nutanix and there solution is new for me. So what I really liked is that Steven didn’t presented a slide deck but just asked what we would like to talk about. Before we knew it, we here in a discussion about the position of Nutanix and there new Acropolix Hypervisor and the impact on existing VMware, KVM and Openstack customers. Although sometimes the filter kicked in about what Steven can and cannot say I really like the discussion. After 1,5 hour Steven noticed that I was time to lunch. And with a few slices of pizza the discussion continued. Steven told us that most of there Acropolix customers (Hypervisor based on KVM) are in Asian and that we only see the top of the iceberg (and than the filter kicked in again 🙂 ).
After more than 2,5 hours we had to go, but where not finished!

Next was Pernixdata with @Frankdenneman. After a tour through there building (including the nice transformed pictures of Starwars characters with the faces of @SatyamVaghani and Frank Denneman) we where offered a beer (it was after 12AM) and went to the boardroom.
Here Frank showed us there latest product FVP Architect. FVP Architect comes with a VIB module in the VMware Hypervisor and is gathering all storage metadata and send this to database where it’s crunched. This gives VMware and Storage administrators realtime and historical overview how there environment is performing and what can be improved. It also gives a in-dept view about what type of storage workload and which virtual machine is generating this workload. Giving you the option to adjust this VM instead of just buying more IOPS for your storage.
After a while we had a discusion about when a virtual machine writes a block of data and how this is handled by the VMware kernel to storage . I had a mis conception that the VMware Kernel alway’s writes in 8Kb block to VMFS (8Kb is used for sub-allocation). So Frank pulled in one of the VMFS inventors @mnv104, and where taught a lesson in how the VMkernel kernel sends data to the storage layer. Woh!

I know Frank has tolled me a lot of times  that most people who where working on the cool stuff in the VMkernel now work at Pernixdata, but now I experienced it!
After a quick visit from Satyam I was time to leave. This was really a cool visit!