Hi! Would it be feasible to run bcache (write-through) with existing ext4 filesystem? I have 400GB of data I'd rather not move, and SSD I could use for caching. Ok, SSD is connecte over USB2, but I guess it is still way faster then seeking harddrive on random access... I have kernels on that partition, so it would be nice if grub2 could still read it, and it would be good if I could go back to old kernel. IIRC ext* filesystems have first 1024 bytes reserved for the bootloader. Unfortunately, cache_sb is bigger than that, and it is normally at offset 4K in the disk. Is cache_sb.d[] being used for backing devices? Could I just make SB_JOURNAL_BUCKETS smaller? Remaining problem is how to invalidate the cache when someone mounts the filesystem without bcache; but I believe that should be possible to check using "last mount time" field in ext4 superblock. bache would save "last mount time" during shutdown, and would just consider the cache stale if someone mounted it in between.... Does the plan look reasonable? Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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