Are eSATA drives hot swappable?

"Your SATA controller (probably integrated in the motherboard) may or may not support this feature. It's likely if you're dealing with a new motherboard that it does. Basically, older motherboards supported something call IDE emulation rather than using native SATA Advanced Host Controller Interface (which does support hot-swapping).

From the Wikipedia article on SATA:

All SATA devices support hotplugging.
However, proper hotplug support
requires the device be running in its
native command mode not via IDE
emulation, which requires AHCI
(Advanced Host Controller Interface).
Some of the earliest SATA host
adapters were not capable of this and
furthermore some older operating
systems, such as Windows XP, do not
directly support AHCI.

...

While the drivers included with Windows XP
do not support AHCI, AHCI has been implemented by proprietary device drivers."

"(re-edited from original statement presuming the difference was eSATA II versus SATA)

An example hot-swap statement from a SATA controller manufacturer, Addonics:

(1) Serial ATA hot swap feature works only with controllers basing on Silicon Image chip set from our inhouse testing. Other controllers that are not Silicon Image based may not support hot swap. You may consider adding one of the Addonics Serial ATA host controllers to your systems to ensure the hot swap capability. New controllers from Intel and other suppliers may finally support this feature. Please verify with your controller manufacturer if you need to have hot swap in your application. Hot swap is supported in Windows 2000 and XP only. On other OS, drive can be removed without crashing system. But replacing with a different drive can result in crashing the OS."