Thanks for the answer.
I have one question. Basically there's the /etc/mke2fs.conf file and
I've created the following stanza in it:
bigdata = {
errors = remount-ro
features = has_journal,extent,huge_file,flex_bg,metadata_csum,64bit,dir_nlink,extra_isize,bigalloc,^uninit_bg,sparse_super2
inode_size = 256
inode_ratio = 4194304
cluster_size = 4M
reserved_ratio = 0
lazy_itable_init = 0
lazy_journal_init = 0
}
It looks like the cluster_size parameter is ignored in such case (I've
tried both 4M and 4194304 values), and the filesystem was created with
64K cluster size (via mkfs -t bigdata -L bigdata /dev/sdb1 ), which is
the default when the bigalloc feature is set.
So it looks like the cluster_size doesn't do anything when set in
/etc/mke2fs.conf . When I used the -C 4M flag (i.e.
mkfs -t bigdata -L bigdata -C 4M /dev/sdb1), the cluster size was set to
4M as it should.
Is something wrong with the cluster_size parameter set in the
/etc/mke2fs.conf file?
----
# mkfs -V
mkfs from util-linux 2.36.1
On 28/07/2021 01.01, Theodore Ts'o wrote:
> On Fri, Jul 23, 2021 at 05:30:13PM +0200, Mikhail Morfikov wrote:
>> In the man ext4(5) we can read the following:
>>
>> Warning: The bigalloc feature is still under development,
>> and may not be fully supported with your kernel or may
>> have various bugs. Please see the web page
>> http://ext4.wiki.kernel.org/index.php/Bigalloc for details.
>> May clash with delayed allocation (see nodelalloc mount
>> option).
>>
>> According to the link above, the info is dated back to 2013,
>> which is a little bit ancient.
>>
>> What's the current status of the feature? Is it safe to use
>> bigalloc on several TiB hard disks where only big files will be
>> stored?
>
> Yes; the places where bigalloc is perhaps not as well tested is
> support FALLOC_FL_COLLAPSE_RANGE, FALLOC_FL_INSERT_RANGE, and
> FALLOC_FL_PUNCH_HOLE. Bigalloc is also not very efficient for large
> directories (where we allocate a full cluster for each directory
> block). Older kernels did not handle ENOSPC errors when delayed
> allocation was enabled, but that has since been fixed, and bigalloc is
> passing file system regression tests, so it should safe to use as
> you've described.
>
> Cheers,
>
> - Ted
>
>
