IBM (IBM) backers are on cloud nine.  

The computer giant's cloud business helped the company top Wall Street expectations, in the first second-quarter earnings report from the leading cloud computing providers.

Shares of IBM were gaining 2.6% to $148.30 on Thursday. The company reported second quarter earnings of $3.08 per share after the close on Wednesday, topping forecasts of $3.04.

However, one rule of thumb in the fast-growing cloud computing sector is that results can be a little ... cloudy. For the last 12 months, IBM said its cloud revenue grew 23%, or 20% adjusting for currency changes, to $18.5 billion. During that time, the company landed new cloud clients ExxonMobil (XOM) , Amtrak and Telefónica (TEF) .

IBM's figure includes $8.2 billion in sales of hardware software and services to companies that are setting up hybrid clouds, which blend privately-operated clouds with services from public cloud providers such as Amazon's (AMZN) Amazon Web Services, Microsoft (MSFT) Azure and Alphabet's (GOOGL) Google Cloud Platform. IBM's revenues from various cloud products billed "as a service" came to $10.4 billion for the last 12 months.

"Similar to several of its peers, IBM doesn't make it clear and obvious from its earnings call material what the scale and trajectory are for the key cloud market segments," John Dinsdale of Synergy Research Group wrote in an email.

However, Dinsdale noted, IBM "continues to do quite well" in cloud infrastructure services. The company maintained its global market share at about 8%, Synergy estimates. 

"Because [IBM] doesn't focus as much on the more glitzy and media-oriented public [infrastructure-as-a-service] segment, it doesn't get the same level of attention and press coverage as AWS, Microsoft, Google and Alibaba (BABA) ," Dinsdale said. "But it continues to do very well in hosted private cloud services and in certain [platform-as-a-service] areas."

IBM's longer-term turnaround remains in doubt, however, as it struggles to de-emphasize slower-growing legacy businesses. Shares are down 8% over the last two years and 23% over the last five years. 

The cloud rankings will be clearer in a week. Microsoft reports after the close on Thursday (TheStreet will be live-blogging the earnings report and call; check our our home page for more details). And next week, Alphabet will provide numbers on Google Cloud Platform on Monday and Amazon will report on its market-leading Amazon Web Services next Thursday.

IBM's Chief Financial Officer James Kavanaugh touted that his firm is becoming "the destination for mission-critical workloads in hybrid environments" during IBM's earnings call after-hours on Wednesday. 

IBM's Strategic Imperatives unit, which includes its cloud business, grew 15% to $10.1 billion in the second quarter and accounted for just more than half of IBM's $20 billion in sales.

While the new, strategic lines of businesses are growing, Jeffrey Kvaal of Nomura in a Thursday report that there is a catch. "Some of the growth in Strategic Imperatives comes at the expense of legacy segments...and legacy seems able to decline just fine on its own," Kvaal wrote.

While IBM is "hardly firing on all cylinders" amid declines in older businesses, Kvaal raised his target from $160 to $170 per share because of confidence that Big Blue can return to "sustained growth."

Kvaal took Kavanaugh's statement that IBM is becoming a "destination of choice" for cloud services with a grain of salt. "While this surely can be debated, IBM did back up its statement by citing competitive wins at Amtrak and Exxon Mobile," he wrote.

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