Gartner has applied its well-known ranking graphic -- the Magic Quadrant -- to cloud IaaS providers.

In a recent report, the research firm said the ranking is focused on providers offering public cloud automation and self-service, rather than on more customized, sophisticated, managed hosting services. Gartner said it also factored in market share in ranking the top 15 IaaS providers.

The result is some surprising selections mixed with some household names. Continue on to see the whole list, ranked by Leaders, Visionaries, Challengers and Niche Players.

Amazon Web Services has a "very pure vision of highly automated, cost-effective IT capabilities, bought without any need to commit to a contract. Its Elastic Compute Cloud is a fixed-size, paid-by-the-VM, Xen-virtualized, public cloud IaaS," Gartner said.

Strengths: AWS is the market-share and thought leader, with the richest IaaS product portfolio, and it is constantly expanding its service offerings, according to Gartner.

Caution: AWS is a "best-effort cloud," according to Gartner. "Its weak, narrowly defined SLA requires that the customer run workloads in at least two AZs [availability zones] within a region; a violation requires that connectivity to both AZs be unavailable. The SLA does not include Elastic Block Store, which most customers use for persistent storage."

Terremark, a Verizon company, gains by leveraging its parent company's data center, cloud and security businesses, Gartner said, and its enterprise cloud can provide multiple VMware-virtualized offerings, including public, managed and public sector clouds.

Strengths: Terremark, thanks to its Enterprise Cloud service, is the market-share leader in VMware-virtualized cloud IaaS, Gartner said.

Caution: Users should be careful to match the service they choose with their particular use case.

Savvis, owned by CenturyLink, is a longtime Web hoster, with a suite of public and private VMware-virtualized IaaS offerings with optional managed services, marketed under the Symphony brand.

Strenths: Savvis' multitiered IaaS product portfolio addresses a wide range of customer needs, and the company has a well-established track record of delivering enterprise cloud services.

Caution: Savvis' large and diverse product portfolio, with multiple types of single-tenant and multitenant IaaS, can be confusing. It offers many narrow point solutions, rather than creating a unified platform for a variety of solutions, according to Gartner.

CSC offers a vCloud Datacenter Service, a VCE Vblock-based cloud IaaS architecture in three variants, Gartner said. It provides public multitenant service in a CSC data center, private single-tenant service in a CSC data center or in the customer's own data center, and optional managed services.

Strengths: Gartner said CSC is one of the few providers offering a standardized architecture across both public and private cloud offerings, as well as a single rate card across all of these offerings.

Caution: The company's cloud division is operated as its own business unit, giving it agility but also occasionally bringing it into conflict with its more staid and slower-moving parent company, according to Gartner.

Dimension Data bought OpSource in 2011 to enable it to enter the cloud IaaS market. It offers VMware-virtualized paid-by-the-VM, public cloud IaaS, as well as suggested-retail-price private cloud IaaS, with optional managed services.

Strengths: Dimension Data can compete against leading cloud providers with aggressive prices, while offering a reliable cloud service. It also has excellent SLAs, including 100 percent availability. It offers AWS API compatibility, as well as its own API, Garnter said.

Caution: The company is still integrating OpSource into its overall portfolio, and although Gartner said it does not foresee business disruptions, business risks remain as the OpSource brand is phased out.

Tier 3, a small service provider, offers paid-by-the-VM, vCloud-powered public cloud IaaS from data centers as well as Database-as-a-Service, and is venturing into Cloud Foundry-based PaaS.

Strengths: Tier 3 offers a good set of features on a well-engineered platform, and has an easy-to-use self-service portal, Gartner said.

Caution: While Tier 3's offering is vCloud-powered, it does not expose the vCloud user interface. Consequently, customers do not receive the full extent of vCloud's self-service capabilities, according to Gartner.

Rackspace offers a fixed-size, paid-by-the-VM, Xen-virtualized public cloud IaaS, with optional managed services. It also offers storage via an integrated content delivery network with Akamai, Database-as-a-Service, and PaaS, Gartner said. As the founder of the open-source cloud management platform OpenStack, its Cloud Builders business provides commercial open-source support and professional services around it.

Strengths Gartner said the company's wide community of participating vendors makes it a key cloud infrastructure ecosystem, up against VMware, Microsoft and Amazon.

Caution: The future of OpenStack's emerging technology is uncertain. "OpenStack's evolution may not necessarily align closely with Rackspace's needs -- it is possible that OpenStack could be successful without it leading to Rackspace's success," Gartner said.

Virtustream focuses solely on cloud services and offers hypervisor-neutral public and private IaaS on its xStream platform, with managed services optional.

Strengths: The company has a strong consultative approach, as well as particular expertise in SAP. Its cloud focuses on production applications, but it targets both traditional enterprise workloads, including ERP applications, as well as cloud-native applications, Gartner said.

Caution: Virtustream supports a solid set of self-service features, but its primary focus is complex, mission-critical applications, "where it is likely that the customer will purchase professional services assistance for implementation, and managed services on an ongoing basis," Gartner said.

Small service provider Joyent focuses on cloud services and offers fixed-size, paid-by-the-VM public and private cloud IaaS.

Strengths: The company emphasizes application performance and includes network-based acceleration. It deploys portal-based performance analytics, using the DTrace framework for application instrumentation, Gartner said.

Caution: Joyent's portfolio of services focuses solely on the hosting use case. Gartner calls it a "best-effort cloud" and said it is very developer-centric. Joyent highlights APIs and the use of third-party tools, rather than its own portal capabilities.

Independent cloud IaaS-focused provider Bluelock aims at the midsize and enterprise markets with a vCloud data center service for public and private cloud IaaS, with optional managed services.

Strengths: Bluelock, as one of VMware's closest service provider partners, is often among the first service providers to deploy new VMware products and version upgrades.

Caution: The provider is small, and while financially stable, its size and excellence of service make it a prime target for acquisition, Gartner said.

GoGrid, according to Gartner, is a small cloud IaaS-focused provider with fixed-size, paid-by-the-VM, Xen-virtualized IaaS as a public cloud and private cloud, with optional managed services.

Strengths: GoGrid is among the top five public cloud IaaS providers in the use of VMs and is one of the few providers that has a standard architecture across its public and private cloud offerings, according to Gartner.

Caution: The company develops its software entirely in-house, which allows it to keep costs down but also results in long-term challenges in competing with providers that can allocate significant resources to R&D, Gartner said.

SoftLayer focuses on SMBs, with CloudLayer, its paid-by-the-VM, Citrix-Xen-virtualized, public and private cloud IaaS. It also provides OpenStack storage with an integrated content delivery network in a partnership with Internap.

Strengths: The company is a leader in automated, standardized, on-demand infrastructure services and has a highly regarded portal, which offers integrated management across its offerings, Gartner said.

Caution: SoftLayer targets self-service for SMB customers, although it is starting to focus on large-scale enterprise deals involving consultative sales, more support and greater flexibility. However, its feature set and road map still serve the needs of SMBs, Gartner said.

OVH, serving SMBs, offers paid-by-the-VM, VMware-virtualized public cloud IaaS, as well as a vCloud Datacenter Service for private cloud IaaS, with optional managed services and object-based storage.

Strengths: OVH focuses on self-service and automation, and is one of the largest European cloud IaaS providers, by VM count, Gartner said.

Caution: OVH's cloud presence is concentrated in a limited data center footprint, although it has recently launched its Canadian data center.

Fujitsu has several cloud platforms, including Fujitsu Global Cloud Platform, multiple local cloud platforms, and multiple private cloud offerings.

Strengths: Fujitsu's history in IT services and data center outsourcing gives it a large base of customers into which to sell cloud services, and has experience extending Fujitsu relationships into cloud deals.

Caution: The Fujitsu Global Cloud Platform is missing some important features, such as access to single-tenant VMs, virtual console access to VMs and the option to bring your own VM images. "Users are likely to find its portal UI to be nonintuitive, and its provisioning times are lengthy compared to other providers," Gartner said.

Dell provides a vCloud Datacenter Service for public cloud IaaS, as well as a VMware-virtualized Dedicated Cloud solution with single-tenant computing.

Strengths: Dell will use a "leverage integration strategy" between its hardware platforms and its cloud offerings, according to Gartner. Dell's hardware business has the potential to lower costs for some hardware components that power its cloud services.

Caution: Dell has no track record in this market. "Its public cloud IaaS offering contains a minimal feature set, and it is missing traits that are critical to enterprise customers, such as the ability to meet compliance requirements and the ability to use customer-provided IP addresses," Gartner said.