If data is saved to disk (standard technology - not obsolete technology filesystems such as FAT), then unexpected power cuts cause no data loss.I'm more concerned with data corruption on my server in the event of a power cut however remote the chances of it happening.
UPS is for temporary (and dirty) power. Hardware protection is not provided by a plug-in UPS. Read its numeric specs to appreciate that. Hardware protection is located elsewhere. UPS does only one function - provide temporary power.