From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp02.belwue.de ([129.143.71.87]:54514 "EHLO smtp02.belwue.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753114AbdHVUsM (ORCPT ); Tue, 22 Aug 2017 16:48:12 -0400 Received: from fex.rus.uni-stuttgart.de (fex.rus.uni-stuttgart.de [129.69.1.129]) by smtp02.belwue.de (Postfix) with SMTP id 4517584D4 for ; Tue, 22 Aug 2017 22:48:11 +0200 (MEST) Date: Tue, 22 Aug 2017 22:48:11 +0200 From: Ulli Horlacher To: Linux fs Btrfs Subject: Re: netapp-alike snapshots? Message-ID: <20170822204811.GO14804@rus.uni-stuttgart.de> References: <20170822132208.GD14804@rus.uni-stuttgart.de> <20170822142451.GI14804@rus.uni-stuttgart.de> <20170822214531.44538589@natsu> <20170822165725.GL14804@rus.uni-stuttgart.de> <20170822180155.GM14804@rus.uni-stuttgart.de> <22940.31139.194399.982315@tree.ty.sabi.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <22940.31139.194399.982315@tree.ty.sabi.co.uk> Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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? > >>> 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:<22940.31139.194399.982315@tree.ty.sabi.co.uk>