Hi Ted, On Thu, Jun 22, 2017 at 08:00:09PM -0400, Theodore Ts'o wrote: > .I make_hugefiles > This boolean relation enables the creation of pre-allocated files as > -part of formatting the file system. > +part of formatting the file system. If the file system is configured so > +that the block group descriptors are located at beginning file system > +space (by using the packed_meta_blocks option), the data blocks of the > +huge files will be contiguous, with the extent tree blocks allocated > +near the beginning of the file system space. It's not quite that simple. The presence of backup superblocks can also cause a discontinuity. If I remove 'num_backup_sb = 0' from mke2fs.conf, I see: PHYSICAL DISCONTINUITY between extents: 2 2 219 220 1073545216 1073577983 1073676288 1073709055 32768 2 2 220 220 1073577984 1073610398 1073709409 1073741823 32415 Also, for packed_meta_blocks to take effect, flex_bg must be enabled. This is documented in mke2fs(8) but not in mke2fs.conf(5). There could be other issues as well; those are just the ones I found. Perhaps there should be an option hugefiles_contiguous which makes the mke2fs command fail if the hugefiles can't be allocated contiguously? Eric
