操作系统书上说，FAT32可管理的单个最大磁盘空间为2TB？我算出来不是2TB。
FAT32格式的文件系统一共有2的32次方=4294967296个簇，每个簇的大小为4KB，
因此可管理的单个最大磁盘空间为4KB*4294967296=2TB
2^32 * 4KB = 16 TB啊？为什么是2TB？
[解决办法]
AT32
In order to overcome the size limit of FAT16, while at the same time allowing DOS real mode code to handle the format, and without reducing available conventional memory unnecessarily, Microsoft expanded the cluster size yet again, calling the new revision FAT32. Cluster values are represented by 32-bit numbers, of which 28 bits are used to hold the cluster number. The boot sector uses a 32-bit field for the sector count, limiting the FAT32 volume size to 2 TB for sector size of 512 bytes and 16 TB for sector size of 4,096 bytes
