CIOs are more challenged than ever to cut costs, do more with less, and "go green" (whatever that means, exactly). But identifying the IT hardware, software, and services that fit the bill is a challenge in and of itself.Harried CIOs can thank Forrester and its Tech Radar methodology for identifying what it calls Green Tech 1.0 technologies -- those that reduce environmental impact throughout the IT asset life cycle. While many of these technologies get a lot of attention, some come with caveats and have landed on Forrester's "survival phase" list:

Cloud Computing -- Public and hosted cloud services such as those from Amazon, Google, Microsoft, and EMC/VMware offer businesses new ways to do more with less despite the technology still being in its early days. Gartner says, however, in a report of its own, that it could be seven years before cloud services reach "mainstream critical mass and commoditization." Actual deployment in enterprise IT, Gartner reports, is only around 5%.

10GbE -- 10 gigabit-per-second Ethernet reduces risk and maximizes gains from server virtualization. But adoption is limited because its per-port price is still between 5x and 10x of 1 GbE.

Solid State Disks(SSD) -- Widely available, but adoption is low so far. Costs are markedly higher than conventional spinning hard disks.

Server Power Measurement -- Few vendors offer commercial software packages for metering at this time. Even those enterprises that do have it won't benefit if they don't use it.

Knowing what's "green" and what its limitations are is the first step toward cutting IT costs, and environmental impact. You've got to start somewhere. Forrester's report is here.