XFS and loss of data when power goes down

"Answer Updated...

XFS is not a data journaling filesystem, such as ext3 and ext4, it is a meta-data journaling filesystem. The result is a trade-off that (usually) favors speed over reliability.

This article has a good discussion of the current state of XFS. When reading, keep in mind all filesystems are compromises between speed and reliability.

Given your lack of control of the situation, you are a good candidate for buying a small UPS."

"for the record, i still frequently see this issue on vms years after...

the bug is not acknowleged by pretty much anyone and most likely comes from idiotic reordering that occur either in the linux vfs layer or possibly in my case in vmware since i've only observed this on vms.

basically the filesystem writes the data to a block and then changes the metadata mapping to point to that block rather than the previously used one, which is then freed.

when operations get randomly reordered in the linux vfs layer in some kind of messy way that involves issuing braind dead reordered transactions while hoping barriers set in the wrong places will help, and additionally using vmware which ignores said barriers, there are little chances things will not end up broken."