Datacenter Fabric for HCI in scale

I'm currently designing a brand new data center based on VMware HCI for one of my customers. Conceptually, we are planning to have two sites in the metro distance (~10 km) for disaster avoidance and cross-site high availability. For me, a cross-site high availability (stretched metro clusters) is not a disaster recovery solution, so we will have the third location (200km+ far from the primary location) for DR purposes. We are also considering remote clusters in branch offices to provide services outside the datacenters. The overall concept is depicted in the drawing below.

Datacenter conceptual design

The capacity requirements lead to a decent number of servers, therefore the datacenter size will be somewhere around 10+ racks per site. The rack design is pretty simple. Top of rack switches and standard rack servers connected to TOR switches optimally by 4x 25Gb link.

Server rack design

However, we will have 10+ racks per site so there is the question of how we will connect racks together? Well, we have two options. Traditionally (Access / Aggregation / Core) or Leaf/Spine. In our case, both options are valid and pretty similar because if we would use Traditional topology, we would go with collapsed Access / Core topology anyway, however, the are two key differences between Access/Core network and Leaf/Spine fabric

1. Leaf/Spine is always L3 internally keeping L2/L3 boundary at TORs. This is good because it splits the L2 fault domain and mitigates risks of L2 networking with STP issues, broadcast storms, unknown unicast flooding, etc.
2. Leaf/Spine supports additional fabric services like automation, L2 over L3 to have L2 across the racks (PODs), Life Cycle Management (fabric level firmware upgrades, rollbacks, etc.), Single Point of Management/Visibility, etc.

We are designing the brand new data center which has to be in production for the next 15+ years and we will need very good connectivity within the data center supporting huge east-west traffic, therefore leaf-spine fabric topology based on 100Gb/25Gb ethernet makes a perfect sense. The concept of data center fabric in leaf-spine topology is depicted in the figure below.

Datacenter fabric

Ok. So, conceptually and logically we know what we want but how to design it physically and what products to choose?

I've just starting to work for VMware as HCI Specialist supporting Dell within our Dell Synergy Acceleration Team, so there is no doubt VxRAIL makes a perfect sense here and it perfectly fits into the concept. However, we need a data center fabric to connect all racks within each site and also interconnect two sites together.

I have found that Dell EMC has SmartFabric Services. You can watch the high-level introduction at
https://www.dellemc.com/en-us/video-collateral/dellemc-smartfabric-services-for-vxrail.htm

SmartFabric Services seems very tempting.  To be honest, I do not have any experience with Dell EMC SmartFabric so far, however, my regular readers know that I was testing, designing and implementing Dell Networking a few years ago. At that time I was blogging about Force10 Networking (FTOS 9) technology and published a series of blog posts available at https://www.vcdx200.com/p/series.html 

However, DellEMC SmartFabric Services are based on a newer switch operating system (OS 10) which I do not have any experience yet, therefore, I did some research and I found a very interesting blog posts about Dell EMC SmartFabric published by Mike Orth aka @HCIdiver and Hasan Mansur. Here are links to blog posts:

• DELL EMC NETWORKING: SMARTFABRIC SERVICES | PART I
• DELL EMC NETWORKING: SMARTFABRIC SERVICES | PART II
• SmartFabrics is Smart for VxRail HCI
• How to enable SmartFabric for VxRail Step 1

So the next step is to get more familiar with DellEMC SmartFabric Services because it can significantly simplify data center operations and split the duties between the datacenter full-stack engineers (compute/storage/network) and traditional network team.

I personally believe, that datacenter full-stack engineer should be responsible not only for compute and storage (HCI) but also for data center fabric. And the traditional networking team takes the responsibility at network rack where the fabric is connected to the external network. You can treat datacenter fabric as a new generation of SAN which is nowadays operated by storage guys anyway, right?

Hope this makes sense and if there is anybody with Dell EMC SmartFabric experience or with a similar design, please feel free to leave the comment below or contact me on the twitter @david_pasek.

New job role - vSAN rulez

Hey, my readers.

Long-time readers of my blog know that I'm working with VMware datacenter technologies since 2006 when I moved from software development to data center infrastructure consulting. In June 2006, VMware released VMware Virtual Infrastructure 3 and it was for me the first production-ready version for hosting business applications. Back in the days, it was a very simple platform (at least for end-users / administrators) and very functional piece of software with huge business benefits.

Let me share with you one secret I have discovered. As I have the software background, over the years I personally developed a lot of software on my own and also in the development teams so there is the law I personally discovered during my developer days in 90' and 2000' ... "The 3rd version of the developed software code is production-ready and to develop three software versions usually takes around 5 years." There are multiple reasons for this statement but this is beyond the scope of this post.

I will just give you two examples related to the topic of this article.

1. ESX 1.0 was released on March 2001 and production-ready (at least for me) was the version ESX 3.0 released on June 2006 ... 5 years of software development and continuous improvements based on customers feedback 
2. vSAN 1.0 was released in 2013 and production-ready (at least for me) vSAN 6.7 U1 in October 2018 ... .. 5 years of software development and continuous improvements based on customers feedback 

But let's go back to the topic of this blog post. Since 2006, I'm dealing with various adventures and challenges with server virtualization and software-defined infrastructure as the whole. It was and still is a very interesting journey and great industry and community to be as the infrastructure principles do not change very often and it was mainly about the better manageability, scalability, and simpler infrastructure consumption for application admins. Well, when I'm saying that key principles in IT infrastructure do not change very often there are few innovations over decades which change the industry significantly.

• Think about "The Flash" (SLC, MLC, QLC, Intel Optane, NVMe) which already changed the storage industry.
• Think about the concept of Composable Disaggregated Infrastructure
• Think about software-defined infrastructures in compute, storage and network

Few innovations mentioned above are changing the technologies but it always takes some time because the most resistant for change are humans. On the other hand, resistance or conservatism if you will, is not always bad because, at the end of the day, the infrastructure is just another tool in the toolbox of IT guys supporting the business.

Well, this is a pretty important thing to realize.

Infrastructure is not here for the sake of the infrastructure but to support software applications. And software applications are not here for the sake of applications but to support some business, whatever the business is. And each business supports some other business. So generally speaking, the quality of the support and simplicity in consumption is the key to have satisfied customers and be successful in any business.

During my datacenter career, I worked for two infrastructure giants - Dell and Cisco - delivering server, storage, and network virtualization consulting to simplify sometimes pretty complex infrastructures. If you ask me for one reason why this is the interesting industry to be, my answer would be - THE SIMPLIFICATION BY ABSTRACTION.

When I look back retrospectively, this is the reason why I have decided to focus on VMware platform and invest my time (13+ years) into this technology. Back then, I have chosen VMware because they were emulating physical infrastructure components as a logical software constructs all backed by API with automation in mind from day zero. Another reason to chose the virtualization abstraction is that I'm a big believer of standardization and commoditization. It allowed me to leverage my existing knowledge about infrastructure principles. The disk is the disk, logically does not matter if it is connected locally through SATA, SCSI or remotely over Fibre Channel, iSCSI. At the end of the day, the disk is there to have a block device on a server and store some data on it. Period. And similarly, you can think about other infrastructure components like NIC, Switch, Router, File Storage, Object Storage, you name it.

My decisions and good intuition always paid back. Nowadays, nobody doubts about server virtualization and business-critical apps and even mission-critical apps are virtualized or planned to be virtualized soon. It's all about x86 commoditization and "good enough" technology. Compare it with another example in ICT. Do you remember the Telco battle between traditional telephone and IP telephony? I do. And do you see such discussions nowadays? No, no. It was accepted as a "good enough" technology even you do not have 100% guarantee you own the line during the telephone conversation. However, it has a lot of other benefits.

And we are in the same situation with PRIMARY STORAGE in datacenters. During the last 10+ years, I was dealing with or witnessing multiple storage issues in various data centers. I'm always saying NO STORAGE = NO DATACENTER. The storage system is a critical component of any datacenter. The major incidents and problems were caused because of

• environment complexity (SAN fan-in / fan-out ratios, micro-bursting, and "slow-drain" issues)
• overloaded storage systems from a performance point of view (any overloaded system behaves unpredictable, even a human body).
• human mistakes

I was witnessing all these issues not only as a data center consultant but also as VMware Technical Account Manager during last 4 years, helping few assigned VIP VMware accounts to keep lights up and think strategically how to simplify data center infrastructures and deliver the value to the business.

Since 2013, VMware is developing the next big thing, software-defined storage. As I've mentioned above, from a technical point of view, I believe vSAN 6.7 U1 is the production-ready piece of software and from now it will be better and better. I'm not saying there are not or will not be any problems. The problems are everywhere around us, the failure is inevitable, but it is about the availability and recoverability options and how fast any solution can be fail-over or recovered. This is again beyond the scope of this article but I hope you understand the point.

Nevertheless, the software eats the world and I believe, there is the momentum for Hyper-Converged Infrastructures which in VMware means vSAN. Of course, it will require some time to convince traditional storage architects, engineers, and operation guys but the trend is absolutely clear. For the transition period, VMware has other storage technologies to leverage not only vSAN but consume traditional storage systems more intelligently with vVols and evolve into software-defined datacenter (SDDC) eventually.

So let me announce publically, that since September 1st, I work for VMware as a Senior Systems Engineer for Hyper Converged Infrastructure (HCI). As a VMware Systems Engineer for HCI, I'm responsible for driving the technical solutions to ensure customer success and revenue goals derived from VMware software and solutions. I'm focused on HCI solutions for assigned Alliance Partner (Dell Technologies) working closely with both the Alliance Partner and VMware technical teams to build the differentiation with that Alliance. I will be also able to bring feedback from the field to VMware and Alliance Product Management teams.

So what you, my blog readers, can expect? More storage-related blog posts about vSAN, vVols, vSphere Replications, SRM, I/O filters leveraged for 3rd party solutions, etc.

I'm excited and looking forward to this new journey. Hope I will have enough spare time to blog about the journey and share it with great VMware community.