> There is a very big and fundamental difference about project id's
> versus user/group id's, and that is that project id's are not first
> class objects in the file system. That is, stat() doesn't understand
> them. Processes do not belong to one (or more) projects, the way they
> do for user and group id's.
Yeah, I totally agree that project ID is different from UID/GID in this
sense. And I think it happens to be why we need project quota rather than
using existing group quota actually.
>
> As a result, project id's are a massive administration nightmare. You
> can't easily see which project a file belongs to, since "ls" and
> "stat" has no support for the project id. So if a file is created in
> one directory, the file will inherent that project id from its parent
> directory. Suppose that file is 100 gigabytes, and it chews up most
> of the project quota for that project. Now suppose that file is moved
> to some other directory.
>
> How in the world is the administrator supposed to find the file which
> is chewing up 100GB of quota? Find doesn't support project id's
> either....
That is the same problem when we are scattering inodes with different
UID/GID into directory-trees. I don't think there is any difficulty in
writing a script to locates the files with a specific project ID. It
might be slightly slower than native find, but I don't think there is
any fundamental difference.
>
> The last time I asked why in the world anyone would want to use this
> feature, the only use case that I heard was people who were using
> containers, and where the all of the project id's were inside a
> chroot. Hence, any questions I asked about what happens when a file
> gets moved out from the hierarchy were hand-waved away, since inside a
> chroot, it could never happen.
I think administrators in HPC or datacenter would like this feature in a
flexible way. I was always getting asked by customers 'how can I know
the spaces/inode used by directoris shared by multiple users/groups'.
'du' doesn't help much because no body wants to wait such a long time if
disk space is at PB-level. In this use case of project quota, I think
it is common for users to move files inside or outside directory-trees.
Regards,
-Li Xi
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
