这个可能是因为VirtualBox工作的时候会反复操作硬盘。如果你的电脑用的是SSD的话，那就悲催了。因为SSD的读写是有次数限制的。这个选项是告诉VirtualBox当前是在工作在SSD环境下，操作硬盘请节制。大意就是这样。

同理，像bt啊开虚拟内存啊这些反复读写硬盘的事，ssd上面都应该关掉。要不会悲催的。

好吧，这个似乎是正解了：

出处：http://superuser.com/questions/327547/virtualbox-solid-state-drive-setting-ok-for-spinning-disks

This just changes whether or not your guest OS sees a solid-state drive (and enables/disables features based on that). Since VirtualBox supports physical pass-through for hard drives, this will only matter ifyou have a solid-state drive on the host computer and have the virtual hard drive on the same drive.

From the guest OS's perspective, all it will do is disable disk defragging, and try to send TRIM commands to the drive (they are ignored if the host drive doesn't support them, or VirtualBox is not using pass-through I/O requests). Aside from that, it's actually up to the SSD controller to choose what sectors to read/write data from/to, not the operating system.

You can turn this on, but you won't see any performance differences. For what it's worth, though, nobody ever has a reason to turn this on unless they are testing SSD-specific features (and even then, can test said features with a simulated SSD).

参考链接：

http://superuser.com/questions/376590/is-running-a-windows-7-vm-on-an-ssd-a-bad-idea