MegaCLI is previous-gen command-line management tool. It is outdated, and not maintained anymore. You can still find it on Avago/LSI web (iirc, 8.07 version), but I do not recommend it. Use newer StorCLI tool instead...
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If you found my answer useful please do *not* mark it as "correct" or "helpful". It is hard to pretend being noob with all those points!