[lustre-discuss] find xdev?

[Michael Di Domenico]

On Tue, Sep 10, 2019 at 5:48 PM Andreas Dilger <adilger at whamcloud.com> wrote:
>
> I don't think "lfs find -xdev" has never been a priority for Lustre, since it is rare for Lustre filesystems to be
> mounted in a nested manner.  Since people already run multiple "lfs find" tasks in parallel on different
> clients to get better performance, it isn't hard to run separate tasks from the top-level mountpoint of
> different filesystems.  What is the use case for this?

doesn't xdev keep find from crossing mount points, not necessarily
only in a nested manner but also if there's a link to a directory in a
different filesystem.  i believe 'find' without -xdev will follow and
descend.  but this predicates that my understanding is sound (which it
probably isn't).  i generally add -xdev to my finds as a habit to keep
from scanning nfs volumes.

> along the same vein, can anyone state whether there's any actual
> performance gain walking the filesystem using find vs lfs find?
>
> For "find" vs. "lfs find" performance, this depends heavily on what the search parameters are.  If just
> the filename, they will be the same.  If it includes some MDT-specific attributes (e.g. uid, gid) then
> "lfs find" can be significantly faster (e.g 3-5x0.  If it is uses file size, then they will be about the same
> unless there are other MDT-only parameters, or once LSOM support is landed (hopefully 2.13).

okay, that's what i thought or recalled correctly from hearing
somewhere else.  in my particular instance i was just using 'find
-type f' and didn't see any appreciable difference in scanning speed
between the two