[pplucky]

I have a 512MB board that does this. If I overclock core_freq by even 1 to 251, I can reproduce ext4 corruption first reboot every time. I have tried different SD cards and it still corrupts.

Just like me. I fixed it by changing the whole STORAGE partition to an USB pen instead and I didn't have a single problem after that.

Yes, but even when using USB it's quite likely you'll be left with an unbootable system if you experience these mmc0 errors when your Pi boots in order to apply a software update (updates to the SD-based kernel.img, bootcode.bin etc.). The only solution (other than avoiding/eliminating the mmc0 errors) is to move /storage to USB/NFS, and apply SD-card based updates manually using a PC (ie. disable auto-update, and never allow the Pi to write to the SD card, basically).

Yes, that is exactly what happens to me... Corruption after each update!

Does this mean that if I either disable the overclock before updating (my past experience shows that this ALWAYS cause corruption in SD card) or manually move SYSTEM and KERNEL files to the SD SYSTEM partition (via PC), it should work?

Any downside of moving these files manually (other than MD5 not being checked)?