Multi-tenant or multi-instance? ServiceNow exposes the debate

SUMMARY:

Multi-tenancy and multi-instance emerged as a discussion topic at a recent ServiceNow event. Brian Sommer unpicks the arguments.

multi-tenantDuring a keynote at ServiceNow’s recent Knowledge 16 user conference, COO Dan McGee discussed how ServiceNow offers a multi-instance solution instead of a multi-tenant cloud solution. I don’t know how much of that went over the heads of the audience but it did catch my attention. And, interestingly, since both approaches have their pros and cons, application software buyers should pay attention to the differences. It could matter to your firm.

Background

In a multi-tenant cloud application, essentially all of the customers share the same copy of the application code. They also have their data stored in a single, shared (and often encrypted) database. When the vendor makes a new release available, there’s only one copy of the code to update and all customers get migrated to the new release simultaneously. Think of how Google changes its search screen imagery on Father’s Day and many other holidays. Every Google customer sees the new version of the screen the next time they access that website. No upgrade CDs/downloads are required. The new version just appears for all users.

There are a lot of advantages to the multi-tenant customer and to the vendor that licenses these applications. For the customer, fewer IT resources are needed to patch, maintain and upgrade the application (reduced TCO). End users get upgraded functionality regardless of what the IT backlog looks like (no delays in receiving new functionality). And, there are no additional hardware and systems software components that must be ordered, installed and maintained (lower TCO, lower capital consumption). For the vendors, there are markedly fewer versions of the software to support (often just the current version and maybe one prior) and far fewer technical architectures to support (often just one). Bottom line: vendors don’t need to charge as much to provide equal or better service to customers and customers can re-deploy a number of IT resources (people, capital, hardware) to more strategic initiatives.

In the private cloud and on-premises worlds, users can have their own copy of the application and their data is stored locally. When a new application version/release is available, the user (not the vendor) is on the hook to upgrade the software, do any database manipulations, convert files, etc.  This environment is great for those companies that want to: heavily customize a packaged application; maintain control over when (or if) the application is upgraded; or, keep their data and software under their total control.

This world is populated with on-premises users, private cloud implementations of cloud software and single-instance cloud solutions. Regardless of the exact deployment, the customers have a unique instance of the software and their data is physically (not just logically) separated from other customers’ data.

This world is expensive for all parties. Whenever a customer has an issue with the software, the vendor may need to recreate the environment that a given customer has. That could mean running an older version of the code on a non-standard relational database, on an operating system that may or may not have recent patches, with a unique combination of systems and security software all on an older piece of computing hardware. Of course, this assumes a vendor can actually create this configuration, has subject matter/technical experts in all of these disciplines, and, can emulate the data that is getting borked. This support environment creates long resolution times and frustrated customers.

Vendors are not too fond of this world anymore. All of those added costs slow their innovation efforts and suck away scarce capital. Just last week, one software executive shared with me that his last employer has to maintain 54 different financial accounting application suites that this company acquired (via mergers/acquisitions) over the years. Worse, this vendor is supporting multiple versions and technical architectures for each of these. This support cost is a major drain on their profitability. It also is siphoning away capital from their innovation/R&D budgets. That last point makes it hard for them to compete with pure-cloud competitors.  This sharp executive now works for a pure-play cloud application vendor – he’s loving his job again.

Multi-instance

What ServiceNow is calling “multi-instance” is a variant of multi-tenancy but with some important twists. What is multi-instance (MI)?

MI is a public cloud deployment of an application where each customer is using their own copy of the software and has their data stored in their own specific RDMBS. It kind of sounds like a hosted, single-tenant solution but ServiceNow, not the customer or a reseller, is on the hook to do software updates, file conversions, etc.

multi-instance

One very, very large ServiceNow customer I interviewed has all of their data on a separate server that is not shared with any other ServiceNow customers. Furthermore, the customer controls exactly when they will upgrade to the next version of ServiceNow.  Poke any big cloud vendor hard and long enough and you’ll often find that they make a couple of architectural concessions to some mega-huge customers. So, I wasn’t surprised to hear of this customer’s configuration of ServiceNow.

That said, ServiceNow does park each customer’s data in a separate database/server combination on their cloud. This has several implications (see below).

What ServiceNow is giving customers via this architecture is:

  • Flexibility in choosing when they will upgrade to new releases. When I pressed them about how much flexibility is really available to customers, their CTO indicated that virtually all customers are kept within a release or two of the current version. As a result, ServiceNow’s customers cannot fall behind materially on new functionality.
  • Physical (not just logical) separation of their data from that of other customers. Isolating a customer’s data to a specific device creates an additional barrier to prying eyes. While encryption technology can achieve much of the same result, this is a physical (not just programmatic) solution.
  • Reduced opportunities for large numbers of customers to be affected by a key system component outage. Readers should see this recent com incident report that shows how a faulty electric switch created havoc for a large number of their public cloud customers. By keeping customer data confined to discrete physical devices, only the customers on that one device are inconvenienced when a fault occurs. In many multi-tenant environments, a single customer’s data could be spread around on several devices and numerous customers can be sharing a single device.

Multi-instance tradeoffs

But this solution presents some tradeoffs, too.

For example, when ServiceNow does an upgrade to its applications, it will need to work through each customer’s unique data store and copy of the software. It’s not applying a single master change to one database – it has to repeatedly apply the same changes to each customer’s database instance. Likewise, it may have to selectively apply the software upgrade to specific users and bypass others.  Multi-tenant vendors don’t always migrate all customers at once either but they tend to move large groups of customers to staging environments based on which upgrade weekend a customer has opted to upgrade upon.

It gets more interesting when you realize that ServiceNow will have customers on a couple of versions of its application software (and possibly database schema). ServiceNow will have to support each of these active versions of the software regardless if the solution has one or a thousand customers running that configuration. That gets expensive and it gets tricky, too, when there are, for example, security patches that must be implemented into all of the different versions.

One big issue I see with this architecture is that it makes the incorporation of big data into an application software suite appear more challenging. All of this choice and database separation is great for traditional transactions but how does it work when different customers want to supplement transaction data with their own specific IoT (internet of things), social sentiment or other big data? This big data is rarely predictable in size, doesn’t always fit well in RDMBS systems and varies immensely among customers. To support big data, these cloud vendors will likely need to create a big-data-instance strategy that shows how alternate data stores/utilities (e.g., Hadoop, in-memory, etc.) will complement the existing ones. I believe it’s solvable but as to how elegant it will be, I’m still wondering. Workday may be further along in this issue than other vendors.  Salesforce is already dealing with massive datasets as social sentiment information is critical to sales and marketing solutions. Other vendors are trying to bolt-on a big data capability to their existing solution without any fundamental rethinking of their technical architecture or customer needs.

Another issue with this architecture is that it could hamper ServiceNow’s ability to provide other aggregated/anonymized benchmarks in the future. For now, the benchmarks they offer cover more systemic metrics (e.g., uptime) and not items like key process times per customer. How they’d easily collect these other data points when customer data is stored in thousands of discrete databases with potentially different data models over multiple servers seems challenging.

The best part of multi-instance

No one seems to write about the challenges present in doing backup/recovery in cloud applications. I bring it up all of the time in software selections I do.

In a nutshell, when you use a cloud application solution, your data is protected by the vendor via a series of tools. They can detect a problem, flip the service to a failover center (that was mirroring your transactions), and, in the event of a catastrophic failure, even recover your (and every other customers’ data). But, what they don’t offer is the ability for just your firm to rollback and recover your information easily.

Why isn’t that offered? To do that in a multi-tenant cloud world, the vendor would have to take down the server/database with your data. Because that server contains your firm’s data as well as that of other customers, ALL customers would be forced offline while your company did a restore. This is not a desirable thing as inconveniencing potentially thousands of customers could hurt the cloud vendor’s image. In some cases, the other affected customers might have to reapply their transactions, too.

Recovery is also tough to do as some solutions run in-memory not off of a RDBMS. And, just to make it even tougher, you (the customer) only get to back up a flat-file of transactions – not an image copy of the production database. Without that database backup, you would have to create a new instance of the software and re-apply every single transaction your firm made since it moved to the cloud service. That’s right, the recovery would invoke an inception-to-date time period not a recovery from the last known clean version of the data.

If some malcontent in your firm blows away your cloud CRM’s customer database (or some less-than-brilliant clerk accidentally deletes a key accounting table), your options to recover are few, expensive and time-consuming. Since every solution is different, be sure to check this issue out in detail with your cloud software vendor.

In ServiceNow’s case, individual customers can halt their instance, do backups, and recover their data to a known point in time. Their actions would not affect other customers. Exactly what tools a customer (or ServiceNow) uses to support this, I do not know.

My take

Years ago, the debate would have been different. The on-premises fan boys and girls would have been attacking the multi-tenant cloud solutions. Those were interesting times when emotion and hyperbole were over-running the facts. But now, most businesses have something in the cloud and even financial institutions are starting to go that way, too. It looks like the cloud will be with us a long time after all.

But which style of cloud architecture will rule the day?

I’ve heard variants of the multi-instance approach before. Unit4 Agresso has had a similar capability for ages. At one time, SAP announced Mega-Tenancy when it launched its Business ByDesign product line. The line between cloud single-tenancy and multi-tenancy is indeed a blurry one. But at least it is all cloud. [Editor’s note: see Phil Wainewright’s discussion of Multi-tenant, multi-instance: the SaaS spectrum.]

That said, I think different approaches to cloud architectures are a good thing as they expose new ideas and options to buyers. They also force vendors to continue their innovation efforts.

Is any individual approach right? No. While I believe that most customers (and vendors) will find the economics behind a real multi-tenant solution to be the best overall (assuming all other factors are constant or equal), I’ve also been unimpressed with the backup/recovery options that some vendors provide here. So, if multi-instance brings some of the best of both worlds together, I’m okay with that.

What I don’t find acceptable are cloud environments where a vendor is supporting too many versions of its product and shows no backbone in standing up to large customers. Too many concessions to larger customers mean that the cost profile of the vendor goes up, innovation speed is lessened, customer service gets hampered, etc.  Balance is the key here as the advantages of public cloud solutions go away when it’s no different than a bunch of single-tenant implementations of various versions of a vendor’s solution.

In the end, the debate is not for me to decide (or referee). It is an issue that prospective customers will decide in the open market.

Image credit - via the author

Disclosure - ServiceNow covered most of the author's travel and expense for attending the event.

    Comments are closed.

    1. Software Guy says:

      What you have described is a single-instance/single tenant solution, there is really nothing “multi” in it.

      There are hybrid variations used to great success including SuccessFactors approach –

      While the core of our approach is multi-tenant with identical database schemas for each customer, SuccessFactors customers are logically segmented at the database level, complete with their own database schema. You can export your own schema out of the database, import or export data, and configure or modify fields. With this approach, we enable individual extensibility within the schemas with our Meta Data Framework (MDF) and XML objects maintained in the identical schemas. SuccessFactors retains all the advantages of a highly scalable and secure multi-tenant model while still offering a highly configurable application. SuccessFactors also provides a distinct application instance per customer, offering better security through enforced memory segregation.

    2. says:

      “It kind of sounds like a hosted, single-tenant solution but ServiceNow, not the customer or a reseller, is on the hook to do software updates, file conversions, etc.”

      1. Phil Wainewright says:

        I’ve added a link in the article to my earlier discussion of these two approaches. As I wrote then:

        … in a modern, virtualized architecture in which databases can be spun up and down on demand, this distinction starts to look as relevant as querying the number of angels that can dance on the head of a pin. As cloud architectures advance, there may be cases where economy is best served by spinning up single instances rather than using multi-tenancy — running web server instances on ARM server processors is one potential example. Therefore it may be that multiple instance will trump multi-tenancy as the defining characteristic of cloud application architectures.

    3. stop promoting the incorrect idea that vendors love: multi-tenancy does not result in cheaper software for users.

      i wrote plenty and wide about why MT is an old idea that needs to be taken back and put out of its misery. there is no value associated with it for users since they lose out on the myriad benefits from being ST and multi-instance.

      this is cloud economics 101 (user side): being able to tightly control how a piece of software executes without losing the granularity of the control as MT does is best for the customer.

      retaining the tight control (which easily leads to lock in) works for the vendor.

      wish we could put this to bed – but vendor hype around “cost savings” (that never exist) won’t let us. sigh.

    4. Thanks Brian for a great article.

      It’s clear to me that multi-tenant is good for the cloud provider while multi-instance is good for the enterprise customer. A few additional thoughts:

      – we believe that the multi-instance architecture gives our enterprise customers the environment that they are looking for in the cloud. Enterprises are used to operating applications in their own facilities where they control the upgrades and have transparency into the environment. Using these enterprise features as a goal, we have built our cloud platform where our customers have a similar level of control over upgrades and transparency into application availability and performance. The multi-instance architecture enables both of these critical features.

      – our multi-instance architecture gives our customers process space separation at both the application tier and database schema level. As you correctly state this entails a level of operations excellence on our side to keep customer instances up-to-date. Thankfully, we have an amazing cloud service automation platform called ServiceNow to use in our environment (and we’re seeing customers who run public and private clouds deploy our platform in a similar fashion).

      – with respect to BigData, we have customers on our multi-instance cloud with 100M+ configuration items (CIs) today (and a few heading toward 1B). To scale to these levels, in nearly all cases we run our customer databases in memory. I’ll concede that as we move into trillions of CIs we may need to add another in-memory technology to our instances but we’re far from needing that today.

      – with respect to backups, you are correct in your description of the service that we provide to our enterprise customers. We use a homegrown backup system driven by our own automation platform.