Before I get started, this post IS NOT a post about why multi-tenancy is a good thing, why it’s better than virtualization, or anything of that nature. I had to get that out before starting – there are plenty of posts that deal with this topic (one, two, three, etc.). Instead, I want to tackle a different issue: the issue of what multi-tenancy means in a variety of contexts as well as how its positioning by vendors is leading to mass confusion.
No particular event has motivated this post; instead, this post is the result of a number of conversations and miscommunications. A while back, I started noticing some disturbing trends in the market, and more specifically, in vendor pitches. Let me use a real world example of what I mean. Frequently, the sales team at Apprenda ends up in the following type of conversation at some point in our sales cycle (clearly, this is distilled for brevity):
Prospect: “I saw that SaaSGrid offers multi-tenancy.”
Apprenda: “That’s right; SaaSGrid gives your application access to various types of multi-tenancy using the same code base and application assets. It’s actually amazingly unique and takes significant effort out of your R&D.”
Prospect: “Yeah, but doesn’t <insert your favorite PaaS/IaaS here> offer multi-tenancy?” or “Well, the folks over at <insert your favorite PaaS/IaaS here> said they offer multi-tenancy too.”
Apprenda: “That’s different. Those technologies are themselves multi-tenant. SaaSGrid is a server technology that allows your single-tenant application to be multi-tenant at all application tiers without the huge effort typically associated with going multi-tenant.
Prospect: “Wait, but that’s exactly what I heard <insert your favorite PaaS/IaaS here> say. You’re saying that they don’t do the same thing as you.”
Apprenda: “Correct. Most, if not all, cloud platform vendors that refer to multi-tenancy are references to their own architectures, meaning they can efficiently pack their customers onto shared hardware/OS instances and offer you better service and a low price point. What you’re asking is how you can be multi-tenant and offer the same to your customers. Others in the cloud can’t help you with that.
Prospect: “OK, so using their service doesn’t make sense then?”
Apprenda: “That’s hard to answer, but it usually makes sense in conjunction with something like SaaSGrid. Clearly, being on something like EC2 (which is multi-tenant at the infrastructure tier) has advantages to you. Using SaaSGrid means you can really lower your internal cost of offering your service to your customers, and either put the savings to the bottom line or pass it along to your customers.”
Prospect: “What SaaSGrid does seems pretty magical now that I’ve cut through the marketing BS, how do you do it?”
Apprenda: “SaaSGrid is a runtime. When deployed to SaaSGrid, your application is transformed and new capabilities are instrumented into all tiers of your application. When running on SaaSGrid, these transformations and runtime instrumentations ‘inject’ SaaS architecture DNA into your non-SaaS web application.”
As you can see, this sort of conversation is a distraction. Whether it’s a conversation with an analyst, industry pundit, or potential customer, I’ve found that the most important thing to do upfront is to level-set on what both sides mean/understand when they say “multi-tenant.” Why so much confusion? I think it’s due to two factors:
- The marketing pitch offered up by vendors and how those marketing sound-bites are contexualized
- The general overloading of the term “multi-tenant”
On the marketing side, vendors do a good job of highlighting multi-tenancy. The problem is that the lack of context around the “feature” of multi-tenancy causes significant miscommunication. From a marketing perspective, vendors are sucked into the Green Crystals Marketing described by Bob Warfield a couple of years ago. Most cloud vendors are touting that they are multi-tenant; they want you to understand that they have a cost-effective and safe mechanism to isolate their customers from one another. To understand this better, I’ve taken the liberty to copy and paste (with references, of course) some content related to multi-tenancy from various cloud vendors:
The AppFabric Container provides base-level application infrastructure such as automatically ensuring scale out, availability, multi-tenancy and sandboxing of your application components. (Microsoft, Windows Azure)
Cloud-enabling infrastructure to allow secure multi-tenant deployments, including fully integrated management, monitoring, metering and billing infrastructure (CloudBees)
If you are running numerous applications/application instances, XAP’s fine-grained multi-tenancy allows you to share them across all available machines, instead of running only one instance per machine. This allows you to support more users on each machine. (GigaSpaces)
There a few others to use as examples, but this is fine for now. I’m not going to debate whether advertising that you are multi-tenant is an effective use of marketing real-estate. all of these snippets of text highlight multi-tenancy, but what is unclear is the context. For example, the first two indicate multi-tenancy at the platform tier; that is, multiple, unrelated code assets can share common OS instances. While this is powerful in its own right, it’s easy to understand how someone reading this text might walk away thinking “Excellent. Our requirements for our new SaaS project call for multi-tenancy. I can check that off our list.” The fact is, while ambiguous in terms of presentation, these technologies do not endow your application with multi-tenancy, they let you run in a multi-tenant environment. If you’re looking to build a multi-tenant app, you need to still architect multi-tenancy (‘architect’ is a verb according to the Oxford English Dictionary). In the gigaspaces case, although they refer to multi-tenancy in a way that lends itself to an “endowment” interpretation, it seems that they are focusing more on a grid approach of scaling the app to support more end users. While this is also valuable, it does not deal with segregation and isolation of logical groups of tenants (which is what multi-tenancy really is). At Apprenda, we even dealt with this definition in problem in our FAQ. This leads me to the next issue: term overloading.
Multi-tenancy is valid in 3 common computing contexts:
- Infrastructure: This is multi-tenancy the way someone like Amazon might refer to multi-tenancy on EC2. In the IaaS context, multi-tenancy means that multiple OS instances can run on the same physical hardware through hypervisor technology.
- Platform: PaaS multi-tenancy means that, like a Heroku or a CloudBees, the platform can isolate code from different apps/vendors on the same OS instance (usually by commingling processes and databases on OS instances). This removes the need to allocate a whole VM per application stack component, improving efficiency.
- Application: SaaS multi-tenancy, at least at the highest level of isolation, means that single runtime stack component instances are shared across multiple customers. For example, a single database might commingle data rows for thousands of customers while preserving isolation and performance.
Clearly, multi-tenancy means different things in all of these scenarios. There is nothing wrong with overloading, but it certainly doesn’t help the already high levels of confusion that exist around the word. If you’re an app developer in the Cloud looking to see what tech can help you, having a sense of clarity is most useful. Make sure you ask simple questions like:
- When you say ‘multi-tenant’, what do you mean?
- If multi-tenancy is a feature of your IaaS/PaaS, does that mean my app automatically becomes multi-tenant and I get to reap efficiencies from it?
- If I want my app to be multi-tenant on your IaaS/PaaS, will I have to still architect the app to be multi-tenant?
If you get answers of “I don’t know” or “No”, then clearly, you’re on your own if you want to build a multi-tenant SaaS app from the ground up.
Do you feel multi-tenancy is thrown around too often by the wrong parties? Is multi-tenancy confusing to you?
