Suffering a power loss while doing ANY sort of high write I/O activity can
potentially cause problems - not just defragmenting. For example, you could
be compacting an access database. This is actually quite rare and depends
on the hardware in use. Along those lines, especially with removable media
(firewall/usb drives), it is sometimes best to disable write caching because
the hardware may not be able to keep up with any high write I/O activity
(not simply defragmenting) and you can have file system issues - even if
there is no power loss.
- Greg/Raxco Software
Microsoft MVP - Windows File System
Disclaimer: I work for Raxco Software, the maker of PerfectDisk - a
commercial defrag utility, as a systems engineer in the support department.
Want to email me? Delete ntloader.
Pegasus (MVP) said:
This is, of course, correct. However, if you suffer an outage
during an ordinary write operation then you may lose the
file you're about to write. If you suffer an outage during a
defragging operation then the damage may be far more
extensive, because of the nature of the operation. I have
dealt with posts that had the whole file system corrupted
(but I have never experienced this myself, perhaps because
I do not see any benefit in frequent defragging).