On Tue 2017-08-22 (19:36), Peter Grandi wrote:

Indeed and there is a fair description of some options for
subvolume nesting policies here which may be interesting to the
original poster:

  https://btrfs.wiki.kernel.org/index.php/SysadminGuide#Layout

It is unsurprising to me that there are tradeoffs involved in
every choice. I find the "Flat" layout particularly desirable.

My layout is already nearly "flat".
It seems my decision was right :-)

Btrfs snapshots can only be done for a whole subvolume.

I know this.

Subvolumes and snapshots can be created by users, but too many snapshots
(see below) can cause trouble. For somewhat good reasons subvolumes
including snapshots cannot be deleted by users though unless mount option
'user_subvol_rm_allowed' is used.

Ooops, this is new to me!

framstag@fex:~: btrfs subvolume create xx
Create subvolume './xx'

framstag@fex:~: btrfs subvolume delete xx
Delete subvolume '/local/home/framstag/xx'
ERROR: cannot delete '/local/home/framstag/xx' - Operation not permitted

This means, root has to remove the subvolme.
Is it possible to disallow creation of subvolumes for normal users?

quoted

quoted

quoted

Because Netapp do it this way - for at least 20 years and we
have a multi-PB Netapp storage environment. No chance to change
this.

Send patches :-).

For waffle or btrfs? :-)

Assumptions that all Btrfs features such as snapshots are
infinitely scalable at no cost may be optimistic:

  https://btrfs.wiki.kernel.org/index.php/Gotchas#Having_many_subvolumes_can_be_very_slow

"when you do device removes on file systems with a lot of snapshots, it
 is unbelievably slow ... took nearly a week to move 20GB of FS data from
 one device to the other using that method"
  
"a balance on 2TB of data that was heavily snapshotted - it took 3 months" 

ARGH!!
Thanks for this warning!
I will overthink my multi-snapshots plan!

-- 
Ullrich Horlacher              Server und Virtualisierung
Rechenzentrum TIK         
Universitaet Stuttgart         E-Mail: horlacher@tik.uni-stuttgart.de
Allmandring 30a                Tel:    ++49-711-68565868
70569 Stuttgart (Germany)      WWW:    http://www.tik.uni-stuttgart.de/
REF:[ref]