I have a question concerning the *hugefiles* parameters. When a
filesystems is created using the hugefiles stanza, it also creates
lots of chunk-* files inside of the /storage/ dir. You say that it
guarantees the huge files to be 100% contiguous. But if I create
the filesystem with the preallocated files that consume the whole
drive, how am I suppose to use that drive? :) Are the files only
temporary, and should they be removed once the filesystem is
"ready"? What's the purpose of such options? Do they affect the
EXT4 metadata in some way? I mean, what's the change compared to
not using the options?
Also I have a question concerning the hugefiles stanza
itself -- it's missing the bigalloc feature, should it be there?
On 29/07/2021 19.59, Theodore Ts'o wrote:
>...
> If you see the hugefile and hugefiles stanzas below, that's an example
> of one way bigalloc has gotten a fair amount of use. In this use case
> mke2fs has pre-allocated the huge data files guaranteeing that they
> will be 100% contiguous. We're using a 32k cluster becuase there are
> some metadata files where better allocation efficiencies is desired.
>
>...
>
> hugefiles = {
> features = extent,huge_file,flex_bg,uninit_bg,dir_nlink,extra_isize,^resize_inode,sparse_super2
> hash_alg = half_md4
> reserved_ratio = 0.0
> num_backup_sb = 0
> packed_meta_blocks = 1
> make_hugefiles = 1
> inode_ratio = 4194304
> hugefiles_dir = /storage
> hugefiles_name = chunk-
> hugefiles_digits = 5
> hugefiles_size = 4G
> hugefiles_align = 256M
> hugefiles_align_disk = true
> zero_hugefiles = false
> flex_bg_size = 262144
> }
>
> hugefile = {
> features = extent,huge_file,bigalloc,flex_bg,uninit_bg,dir_nlink,extra_isize,^resize_inode,sparse_super2
> cluster_size = 32768
> hash_alg = half_md4
> reserved_ratio = 0.0
> num_backup_sb = 0
> packed_meta_blocks = 1
> make_hugefiles = 1
> inode_ratio = 4194304
> hugefiles_dir = /storage
> hugefiles_name = huge-file
> hugefiles_digits = 0
> hugefiles_size = 0
> hugefiles_align = 256M
> hugefiles_align_disk = true
> num_hugefiles = 1
> zero_hugefiles = false
> }
