當愈來愈多的資料被產生出來，我們就需要製造更多空間來存放這些資料，在私有雲以及公共雲的出現後，混和雲在這段時間逐漸地活躍起來；在這裡我們將混合雲視為第三種儲存空間的選擇，我們建立了一個混和雲費用計算模組，並發現在適當的設定下，混和雲長期運作下可以達到比私有雲更低的成本；我們同時也建立了一個搭配抹除碼的可用性模組，在這模組之下，混和雲可以在有效減少資料冗餘的情況下，達到更好的可用性以及安全性；最後我們將兩個模組結合起來一起分析，得出混和雲可以同時有利於上述所有條件。

As more and more data generated every moment, more space is needed to store these data. After the appearance of private cloud and public cloud, Hybrid cloud system becomes more and more famous recently. Here we make the hybrid cloud being the third choice for data storage. We build a cost model to prove that with appropriate settings, hybrid cloud has lower cost than private cloud in a long run. We also introduce an availability model with erasure code. With this model, hybrid
cloud can guarantee higher availability and security with lower data redundancy. In the end we combine both models to prove that hybrid cloud is beneficial for all the features.

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