G. Morgan wrote:
> http://cgi.ebay.com/ws/eBayISAPI.dll...m=150340223444
It creates a file which is a container for a virtual hard drive. Writes
to the real drive are redirected to the virtual drive. When you reboot,
the virtual drive is discarded (or overwritten) so you start from
scratch. Your real drive in its current state is the baseline state,
writes are redirected to the virtual disk, and on reboot the baseline
state is restored. This is how the software virtualization utilities
work, too, like Returnil, DeepFreeze, ShadowStor, and SteadyState.
If there is a mechanical problem with the hard disk, like troubles
reading sectors, that causes file corruption then the file used for the
container for the virtual drive can also get equally corrupted. While a
reboot would eradicate the changes stored in the virtual drive, the
corruption would recur on the container file which means you end up with
corrupted files within the virtual drive.
Its firmware within the chips on the PCB does in hardware what the
software virtualization products do. Because it similarly creates a
container file for the virtual drive, it must understand the file system
for the partition in which it creates the container file. This card
says it supports MS file systems, like FAT and NTFS. That means you
cannot use it to do similar virtualization for a Linux partition. It
uses a driver to perform the write redirects. Presumably it runs as a
kernel-mode drivers to perform file I/O. The question becomes whether
this driver only handles intercepts of system API calls which means any
program that directly modifies the files will cause problems (but then
it is unlikely you'll get such utilities to run within NT-based versions
of Windows but you could under DOS and 9x-based Windows).
I sincerely doubt their claim "No hard disk performance loss".
Additonal stacking of file I/O handlers always incurs a performance
penalty. It is also unlikely that the hardware on this PCB matches the
top-end hardware used in gaming or high-performance hosts so its code to
handle the file I/O in its firmware won't be as fast as the hardware in
the host.
That they call it a "recovery" card is misleading. It doesn't recover
anything. It protects the OS partition by redirecting writes to a
virtual drive inside a file container on the existing hard drive. When
you reboot, those changes are lost and you start from the baseline state
again (your hard drive + new virtual drive). SteadyState, Returnil, and
other software-based virtualization utilities don't recover anything
another than *return* the host back to its baseline state. Think of it
as a System Restore on steroids but with only one snapshot (i.e., you
get to make changes to the virtual drive but you only back to the
baseline state on reboot if you elect to do so, and you don't get to
pick from various states or snapshots saved at different times). You
move forward your baseline state, like to apply Windows updates, by not
enabling their virtualization so changes do get saved into the real file
system, but you have just one snapshot to which you can return.
I looked at these cards many years ago. I decided against using them
and just use the free software products to do the same thing. You do
have to install a driver within this hardware-based virtualization
product but I suspect that no software needs to be installed. To some,
this has the advantage of not polluting their OS partition with this
software. Put on an anti-static strap, power down, open up the case,
stick in the card, close the case, and power up. Then install their
driver and you're probably done. It does require that there is an
available slot which may not be the case since newer mobos have
typically reduced their slot count due to all onboard functions (audio,
perhaps video in south bridge, NIC, USB, firewire, etc).
The Winbond W89C940F chip on their PCB is a LAN controller. That's
because you can remotely administer those hosts. That wasn't something
that interested me for the software-based virtualization products so I
don't which ones provide that feature (but then it probably is
considered an enterprise function and available on in the payware
versions of those programs).
For this hardware product, their manual recommends disabling your
anti-virus and other anti-malware products and any imaging/ghosting
programs used for backups. They're incompatible with the virtualization
used by this hardware product (but I haven't encountered a problem with
the software products).