回复：计算机要加一块硬盘，各位帮助参谋一下，

external hard drive is better:
convenient.
even faster than some internal hard drive.
average seek time=8~9ms
data transfer rate >200MB/Sec.
only thing is more expensive.
it is a little hard to install internal, depends on the controler, may need to specify master and slave if share a controler.