RAID是什么？
摘自维基：

RAID (redundant array of independent disks, originally redundant array of inexpensive disks[1][2]) is a storage technology that combines multiple disk drive components into a logical unit. Data is distributed across the drives in one of several ways called "RAID levels", depending on what level of redundancy and performance (via parallel communication) is required

三个基本作用：: resiliency, performance, and capacity.

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据高人说，应用服务器等可以用RAID1, SVN服务器可以用RAID5，而数据库理想情况下应该用RAID10