From owner-freebsd-questions@freebsd.org Wed Nov 8 13:42:48 2017 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E02BEE53DB8 for ; Wed, 8 Nov 2017 13:42:48 +0000 (UTC) (envelope-from ml@netfence.it) Received: from smtp205.alice.it (smtp205.alice.it [82.57.200.101]) by mx1.freebsd.org (Postfix) with ESMTP id 7A0C77AD0F for ; Wed, 8 Nov 2017 13:40:20 +0000 (UTC) (envelope-from ml@netfence.it) Received: from soth.ventu (82.57.190.113) by smtp205.alice.it (8.6.060.28) id 5A00FE8B00633F15 for freebsd-questions@freebsd.org; Wed, 8 Nov 2017 14:39:57 +0100 Received: from alamar.ventu (alamar.local.netfence.it [10.1.2.18]) by soth.ventu (8.15.2/8.15.2) with ESMTP id vA8DduJn003399 for ; Wed, 8 Nov 2017 14:39:56 +0100 (CET) (envelope-from ml@netfence.it) X-Authentication-Warning: soth.ventu: Host alamar.local.netfence.it [10.1.2.18] claimed to be alamar.ventu From: Andrea Venturoli Subject: Maximum number of UFS snapshots To: freebsd-questions@freebsd.org Message-ID: <8453ff76-0340-16c5-35b2-341ae6367606@netfence.it> Date: Wed, 8 Nov 2017 14:39:51 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 08 Nov 2017 13:42:49 -0000 Hello. I read an UFS filesystem can have up to 20 snapshot. Looks like this is fixed in the kernel sources(*) and cannot be increased. (*) sys/ufs/ffs/fs.h reads: > /* > * The maximum number of snapshot nodes that can be associated > * with each filesystem. This limit affects only the number of > * snapshot files that can be recorded within the superblock so > * that they can be found when the filesystem is mounted. However, > * maintaining too many will slow the filesystem performance, so > * having this limit is a good idea. > */ > #define FSMAXSNAP 20 I wonder if this is something that can be changed. Leaving performance considerations aside, what would this imply? Inability to read previously formatted UFS filesystems? Impossibility to share UFS filesystems with other machines? Superblock growing beyond its maximum size? Anything else? bye & Thanks av. P.S. This is mainly out of curiosity. Although such a FS would fit my needs, I'm not reckless enough to try this in production :)