Ted speaks again
Posted Mar 16, 2009 16:54 UTC (Mon) by kleptog
In reply to: Ted speaks again
Parent article: Garrett: ext4, application expectations and power management
Try explaining to your grandma or to the guy down the street running a Moblin netbook that their system is not bootable anymore, or they can't use most of their applications, because POSIX doesn't give a shit that users get half their file system blown away when they shut their devices down incorrectly.
Honestly, I don't see why POSIX should care. It's a standard that describes an API that can be used by programs that wish to be portable. In principle it could be implemented on anything from the smallest handheld to the largest mainframe. Reliability after a crash is outside the purview of POSIX since the requirements are vastly different in different situations. People writing software for embedded devices don't rely on POSIX to give them crash safety, they read the manuals for the device to see what the manufacturers say they should do.
POSIX compliance is a property of the OS-userspace boundary, crash-safety is a property of an entire system. They're largely orthogonal.
In my opinion it's wrong for people to say that either behaviour is mandated by POSIX.
IMHO it's neither mandated nor forbidden. Crash reliability is a contract between you and the OS+hardware+kernel. A ramdisk can be POSIX compliant yet is clearly not crash safe. Leave POSIX out of it, decide what Linux wants to guarantee. POSIX provides a way of guaranteeing a certain reliability but Linux is free to provide additional guarantees if it sees fit.
Maybe something for LSB? I'd like to see the language lawyers work out a way of defining "crash-safety" in a way that doesn't exclude things like ramdisks and several existing filesystems.
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