On 2012-09-28, Ilyas -- <umask00 at gmail.com> wrote: > > One day our servers farm rebooted unexpectedly (power fail happened) > and on centos 6.3 with up2date kernel we lost few hundred files (which > probably was opened for reading, NOT writing) on XFS. > > Unexpected power lost follow to situation when some files get a zero size. No filesystem can fully protect against power failures--that's not its job. That's why higher-end RAID controllers have battery backups, and why important servers should be on a UPS. If you are really paranoid, you can probably tweak the kernel (e.g., using sysctl) to flush disk writes more frequently, but then you might drag down performance with it. IOW, it's nice to have fsck, but it's better to take steps to avoid needing it. That being said, through a series of unfortunate events, I've lost power on some of my larger XFS filesystems, and in those rare events I have not seen or heard about any files lost. So I strongly suspect other factors in your data loss--if XFS was involved, there were probably also other issues involved as well. --keith -- kkeller at wombat.san-francisco.ca.us