The standard Angstrom image on Beaglebone uses ext4 as its rootfs on a SD card. As I understand the controller internal to SD cards do not behave well if power is removed when writing. It therefore seems that a journaling file system such as ext4 provides little or no benefit for power interruption, and may increase wear due to additional writes to the journal. I would have thought that ext2 may be a better choice. Am I missing something here?
Regards,
Dave.
The standard Angstrom image on Beaglebone uses ext4 as its rootfs on a SD card. As I understand the controller internal to SD cards do not behave well if power is removed when writing. It therefore seems that a journaling file system such as ext4 provides little or no benefit for power interruption, and may increase wear due to additional writes to the journal. I would have thought that ext2 may be a better choice. Am I missing something here?
What makes you think journalling doesn’t work on SD cards?
I am sure that journaling work on SD cards. My point is that if the underlying block structure fails on power loss, then any data to the journal at the time of power fail may increase the likely-hood of device failure. I understand from other posts that some SD internals, dependent on manufacturer, are “optimized” for FAT-like sequential writes. Maybe I am misinformed here, but I am having difficulty understanding the mechanism by which my root file systems are being corrupted on power cycles. I have used UBIFS on raw NAND with much lower failure rates than ext4 on SD cards.