The reality of cloud computing has always been a lot more about the nuts and bolts of data-center operations than about the metaphor of on-demand \n\ncomputer power flowing from anonymous sources somewhere on the other end of the network connection. Cloud Computing Definitions and SolutionsStill, it's a bit too meta when you realize that cloud-computing platforms are often made up of other clouds. OS-independent virtual application-appliance vendor AppZero, for \n\nexample, built its service on the existing IaaS (Internet as a service) offering from GoGrid, which itself is an owned spinoff of traditional data-center hosting provider ServerPath. The Source for the ForceSaaS groundbreaker Salesforce.com runs entirely from data centers owned by Equinix, one of the world's largest co-location and data-center hosting providers\u2014whose 2800 customers include hundreds \n\noffering cloud-based infrastructure, application or content services using Equinx' 50 data centers as a base. Equinix co-location competitor Rackspace bought virtual-private-server provider Slicehost, online storage provider JungleDisk and e-mail service Webmail.us to help it compete\u2014primarily in the consumer and SMB \n\nmarket\u2014against infrastructure-as-a-service providers such as Amazon.Oddly, both Rackspace and Amazon's S3 service rely on Equinix data centers, though to differing degrees. Amazon's cloud billows entirely from \n\nEquinix facilities, while Rackspace rents space, bandwidth or compute power only in locations it has no facilities of its own. Much of the rest of the \n\nInternet's data- and content-backbone runs from Equinix, however, including services from Citrix Online, AT&T Verizon, MSN, Level3 Networks, \n\nAbout.com, Akamai, America Online, Electronic Arts, Yahoo and Paypal.Companies such as Terremark \u2014 which offers one cloud service for small groups and another for enterprises \u2014 are more impressive \n\nin many ways than Equinix, which only provides the platform, Mark Kelleher, managing director of financial analysis firm Brigantine Advisors told the Wall Street Transcript. \n\nEquinix has turned itself into an enabler of both cloud providers and carriers, building itself a vendor-neutral business in the process, however, \n\nKelleher says. As a pure infrastructure specialist, however, Equinix can focus on its own technology and add value by putting together customers who can offer \n\none another the kind of specialty services they'd otherwise have to build themselves, according to Vince DiMemmo, general manager of cloud and IT \n\nservices at Equinix. "Services that are running in the cloud need some pretty intense network connectivity on the backbone, broad network services for service delivery \n\nand cost management, high physical security and availability \u2014 five nines or higher," DiMemmo says. A New Kind of IT Service Provider"A SaaS company can come in to one of our data centers and employ a co-location model and provide all their own services on top of that, but \n\nthey could also connect to other cloud providers for that," DiMemmo says. "Because we focus so much on network service providers, what you see in \n\nthe data centers is an ecosystem they can plug in to for hardware and software and networking that is optimized for fast throughput without having to \n\nbuild it themselves."The cloud phenomenon is changing the way IT service providers of all kinds define themselves, moving them away from their traditional role as \n\nintegrators of technology, and into the position of developing the technology they sell, according to Gartner analyst Lydia \n\nLeong.With a long list of expansions, \n\nacquisitions and new services designed to give telecommunication companies a \n\nlow-latency, high-bandwidth way to pass IP traffic among their networks, Equinix is going the other way \u2014 sticking with the infrastructure rather \n\nthan ways to distribute content or \n\nother services on top of it, she wrote. There's not much mystery to data center management, but it's an unrelenting and unforgiving business, according to Bob Laliberte, analyst at the \n\nEnterprise Strategy Group. That's why VMware, BMC, IBM, Cisco and other major players in the virtualization market began making agreements early last year \u2014 \n\nwhen VMware's push for internal clouds rather than simply virtual server networks was in its early stages, Laliberte says. Ever since offshoring got hot in the '90s, large companies have been moving toward a model of IT in which the IT services appear to come from a \n\nsingle IT department but are actually an integrated mix of cloud, virtualization and networking services, often provided by external companies, according \n\nto Chris Wolf, analyst at The Burton Group. The best thing about cloud computing isn't that you can add or subtract compute resources according to demand from your own users, according to \n\nSteve Peltzman, CIO of the Museum of Modern Art in New York. The best thing is that clouds make it much easier to plug in new services without months of development and testing, making it possible for even \n\nsmall IT shops to offer sophisticated applications and services, he says.Who knew the cloud providers would build their services the same way?Follow everything from CIO.com on Twitter @CIOonline.