One nagging question for Microsoft continues to be just how big its “pure” Azure cloud business is compared to its profitable, but less sexy, traditional software business. And, like many Microsoft execs before her, chief financial officer Amy Hood deftly sidestepped that inquiry on Tuesday.

Microsoft recently claimed a hefty 140% growth rate for Azure revenue. So, the inevitable questions for Hood at the Morgan Stanley Technology Conference in San Francisco this week were how much of that money is really new business for Microsoft msft and how much derives from current customers shifting software purchases from on-premises to Microsoft’s cloud.

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Hood was prepared, noting, “I focus on overall growth. We want to incent cloud-selling of course, but for us it’s going at the pace the customer wants.” Many Microsoft customers will keep running Windows Server and Exchange on-premises, while others will want to run some Microsoft code in-house along with the Azure public cloud in a hybrid model. Perhaps some will want to shift lots of work to Microsoft-owned-and-managed Azure public cloud.

Public clouds à la Azure, Amazon Web Services, and Google Cloud Platform comprise massive pools of computer servers, storage, and networking that customers can rent for their own IT needs. Often companies use public cloud to supplement their own infrastructure so they don’t have to build more of their own data centers.

From Hood’s point of view, some of Microsoft’s growth stems from the cloud and some from sales of on-premises software. So there.

Also read: Microsoft CEO Satya Nadella Q&A

She reiterated that some Microsoft products blend on-premises and public cloud models. For example, customers can run Microsoft SQL Server database on their own servers but use Azure to back up that data.

“If overall opportunity is growing and you can take share, it’s growth,” she added.

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This sounds like a typical marketing spiel, but it is true that Microsoft, unlike Amazon amzn Web Services (the public cloud leader), can support this balancing act. Customers can run Azure Pack internally so their own data centers that mirror the Azure public cloud. That’s a plus for companies who may like the idea of renting capacity on Amazon Web Services or Google goog Cloud Platform but want to have an off-ramp if things go south.

No matter what any cloud provider says, shipping data off its infrastructure is onerous—both in terms of time and money. In this way, the public cloud is sort of like a roach motel: You can check in, but once there, it can be hard to leave.