Companies are sometimes choosing software-as-a-service over on-premises software because it is inexpensive and flexible, yet recent outages at Google and Workday are reminders that SaaS isn't perfect. SaaS lets CIO pay only for what they need, but how do CIOs make sure they get the performance they've paid for?

Most SaaS vendors only guarantee 99.9% availability or better, depending on the app, because in any IT infrastructure, unplanned outages can and do occur. But a good SaaS vendor, in addition to presenting a solid fail-over plan, is forthright about system performance, and communicates the details of unplanned outages if they occur.

Ray Wang, an analyst with Altimeter Group, published a best-practices document for SaaS earlier this month, titled "Customer Bill Of Rights: Software-as-a-Service." On performance metrics, Wang advises that SaaS customers should expect their vendors to provide a "trust site" for monitoring service levels (such as Trust.salesforce.com or status.netsuite.com), although not all vendors provide such sites. Vendors also should provide a monthly report on key availability and continuity metrics, Wang advises.

Workday, which offers human resources, financial apps, and payroll-as-a-service, is among those that don't offer a trust site. But it's still a small company, with only 100 customers, so it was easy enough to call or e-mail customers with status updates during a 15-hour outage on Sept. 24.

A network-attached storage device that stored operating system files for Workday's production servers self-diagnosed a corrupted mode. But rather than simply logging it, the device took itself offline. When Workday couldn't resolve the problem within a few hours, it began the 12-hour process of moving its systems over to a back-up data center.

These details were provided to customers during the outage. "The communication from Workday was frequent and fairly complete," said Andy Schlei, VP and divisional CIO at Sony Pictures Entertainment. Sony is a new Workday customer for human resources SaaS. Sony is still running it in a test environment, so its HR operations weren't affected by the outage. Still, news of it was "disappointing," said Schlei. "It's not good to have an outage like this. But, there was no data loss, there was a reasonable amount of time for recovery, and they clearly communicated the root cause."

Indeed, transparency is key to successful SaaS relationships, said Wang. At a Workday user conference on Oct. 19 in San Francisco, Wang said he talked to several Workday customers about the outage. "For the most part, customers who got those phone calls from Workday throughout the night were very understanding, because Workday was pretty up front about it," he said.