Table:
| ($ in millions) |  |  |  |  |
| --- | --- | --- | --- | --- |
| For the year ended December 31: | 2018 |  | Yr.-to-Yr. Percent Change | Yr.-to-Yr. Percent Change Adjusted for Currency |
| Systems external revenue | $8,034 | $8,194 | (2.0)% | (2.3)% |
| Systems Hardware | $6,363 | $6,494 | (2.0)% | (2.3)% |
| IBM Z |  |  | (5.4) | (5.6) |
| Power Systems |  |  | 8.8 | 8.7 |
| Storage Systems |  |  | (5.5) | (5.9) |
| Operating Systems Software | 1,671 | 1,701 | (1.7) | (2.4) |
Paragraphs:
Systems revenue of $8,034 million decreased 2.0 percent year to year as reported (2 percent adjusted for currency) driven by strong IBM Z performance in 2017 and continued price pressures impacting Storage Systems in a competitive environment.
Both hardware platforms were down year to year for the full year, as reported and adjusted for currency. This performance was partially offset by strong growth in Power Systems (which grew as reported and adjusted for currency in 2018) with strong performance in POWER9-based systems and Linux throughout the year. Within Systems, cloud revenue of $3.1 billion decreased 10 percent as reported and adjusted for currency compared to the prior year reflecting IBM Z product cycle dynamics.
Question:
What factors led to growth in Power Systems 
Answer: strong performance in POWER9-based systems and Linux throughout the year.