I have a system running linux that must run unattended for long periods of time. The system uses industrial CF card for storage. Most of the time there are no writes to flash, although every now and then some configuration data/settings can be modified. The system must be resistant to power failures.
I would like to use ext4 for this. What is the best way to configure ext4 for this kind of setup? Bearing in mind that:
- Performance is not a problem at all (especially write performance)
- Upon power loss, the system should always boot in a clean state, even if that means that data written in the last few seconds is lost
- If it is possible to avoid fsck, then all the better.
(I am aware of this related question:
Prevent data corruption on ext4/Linux drive on power loss)
Answer
I've worked in building a system for automation on boats, and there was a prerequisite: in every moment the power could go down and everything must boostrap again correctly.
My solution was to build a Gentoo-based initramfs system, with only a rw folder for application and configurations (this is the approach used by every router/firewall vendors). This solution add an additional layer of complexity when dealing with system upgrades, but assure you that the system will ALWAYS boot.
Regarding your specific question, you should keep EXT4 journal enabled for having faster fsck (of a few secods), use the data=journal mount option, lower the commit option or use sync option to keep buffers always empty.
Refs: http://www.kernel.org/doc/Documentation/filesystems/ext4.txt
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