This functionality improves the chances that sequentialdisk blocks are allocated, because the total number needed will be known.
这样所需磁盘空间总数就一目了然，因此这个功能提高了分配连续磁盘块的可能性。
2
For random accesses, the performance penalty can be ignored, and for sequentialdisk accesses, there are about 7-28% performance degradation.
对于随机读写安全所造成的性能损失几乎可以忽略不计；对于顺序读写，性能下降了7% - 28%。
3
It is very important to distribute data horizontally across multiple containers so that with a high number of sequentialdisk reads, all disk spindles can move in parallel.