Only with a UPS

Posted Sep 12, 2009 0:35 UTC (Sat) by spitzak (guest, #4593)
In reply to: Only with a UPS by ncm
Parent article: POSIX v. reality: A position on O_PONIES

You are wrong.

While the power is still running, and the disk is spinning and working perfectly, EXT4 has *already* stored information on it that says the file that the atomic rename() went to is empty. The disk is in the wrong state! It is irrelevant whether a power failure may further damage the data!

Only with a UPS

Posted Sep 12, 2009 6:22 UTC (Sat) by ncm (guest, #165) [Link]

You rather miss the point. Given reliable storage -- i.e., doesn't lie about what's reached disk, or has enough battery backup to make sure it gets there, eventually -- it's possible to write a reliable file system. Without, it doesn't matter how well done the file system is, a power drop can corrupt it. If you want safety against power drops, you need both.