On Jul 23, 2021, at 9:30 AM, Mikhail Morfikov [off-list ref] 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?

Hi Mikhail,
I am not using bigalloc myself (and I'm not aware of its use with
any Lustre-releated ext4 filesystems), but I believe that bigalloc
is in use at some other large storage sites.  Hopefully someone
that is using it can respond here (this may be slow due to summer
vacation).

Cheers, Andreas