It is best to use the "Safely Remove" icon at the bottom
of your screen. That prepares the OS for the removal of
a data drive.
Safely Remove should refuse to release the boot drive.
If you unplug a SATA boot drive, without successfully
using Safely Remove, then you'd be relying on the NTFS
journalling capability, to undo the damage. You could
even lose the most recently written file by doing that.
SATA hot plug doesn't work with all possible drivers.
There are some driver options which don't support
hot plug. So an attempt to add a SATA drive to such a
computer, while the power is on, could result in
the drive being ignored. On some Intel chipset
machines, the AHCI driver is one way to get
hot plug capability. So some planning goes into
making sure a new computer will be prepared
for hot plug and unplug of SATA.
USB flash memory uses some similar rules. "Safely Remove"
is used for those as well. The driver that comes with the
OS, provides all necessary functions. There is no planning
to do, before using that.
A lot of brand new computers, are using AHCI as a default,
and so hot plug is there when you take delivery. For older
hardware, there is some planning to do, to make SATA
hot plugging work.
You CAN but shouldn't! Amongst the many problems that can happen is you
unplug it during a write cycle, trashing an area of the disc, or perhaps
buffers have not yet been written out to disk, so programs you closed aren't
on the disk as closed and the OS locks up when it does finally try to write
them, or the data in the buffers will be lost, etc.. Either power down the
computer or use the safely remove icon if it'll work; sometimes it won't
work, simply because it knows there are buffers that haven't been written to
the disk yet and other reasons too.