On Sep 11, 2009 10:18 -0500, Eric Sandeen wrote: > Pointing debugfs from the pu branch at a large filesystem is > still failing with: > > Filesystem too large to use legacy bitmaps while reading block bitmap > > We need to open with EXT2_FLAG_64BITS; I'm not sure if this > should be a switch based on the size of the fs or not? The one thing that is already VERY painful is the time it takes for debugfs to read the bitmaps from disk at startup. Running with "-c" allows that step to be skipped, but tha means it isn't possible to modify the filesystem at all. The time for 8TB filesystems is already in the multi-minute range, so I can't imagine how long it will take on huge filesystems. The only saving grace might be flex_bg avoiding seeks between every pair of bitmaps. Has any attention been given to the ext2fs_load_bitmaps() function for flex_bg filesystems? This would need to be tuned to read groups_per_flex block bitmaps first, then groups_per_flex inode bitmaps before skipping to the next flex group. Otherwise we may still be reading each pair of block+inode bitmaps at a time, and only by virtue of disk track caching are we avoiding a seek between each one (which would eventually break down once the groups_per_flex exceeds the track cache size). Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
