From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A08A1C4708E for ; Sat, 29 May 2021 09:53:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D26B6127C for ; Sat, 29 May 2021 09:53:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229597AbhE2JzU convert rfc822-to-8bit (ORCPT ); Sat, 29 May 2021 05:55:20 -0400 Received: from mail.am-soft.de ([83.218.36.120]:59192 "EHLO mail.am-soft.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229559AbhE2JzT (ORCPT ); Sat, 29 May 2021 05:55:19 -0400 Received: from mail.am-soft.de (localhost [127.0.0.1]) by mail.am-soft.de (Postfix) with ESMTP id CC58E3B6EAE0; Sat, 29 May 2021 11:53:41 +0200 (CEST) Envelope-To: linux-btrfs@vger.kernel.org Received: from Bit02EX.bitstoregruppe.local (exchange01.bitstore.group [116.202.141.225]) by mail.am-soft.de (Postfix) with ESMTPA id BA9213B6EADE for ; Sat, 29 May 2021 11:53:41 +0200 (CEST) Received: from tschoening-nb.fritz.box (77.78.163.99) by Bit02EX.bitstoregruppe.local (192.168.254.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Sat, 29 May 2021 11:53:37 +0200 Date: Sat, 29 May 2021 11:53:30 +0200 From: =?utf-8?B?VGhvcnN0ZW4gU2Now7ZuaW5n?= Organization: AM-SoFT IT-Service - Bitstore Hameln GmbH i.G. Message-ID: <1806742121.20210529115330@am-soft.de> To: Subject: Re: How does BTRFS compression influence existing and new snapshots? In-Reply-To: <20210528193612.GE11733@hungrycats.org> References: <1743059466.20210528180204@am-soft.de> <20210528193612.GE11733@hungrycats.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-Originating-IP: [77.78.163.99] X-ClientProxiedBy: Bit02EX.bitstoregruppe.local (192.168.254.21) To Bit02EX.bitstoregruppe.local (192.168.254.21) X-C2ProcessedOrg: e1a4acb5-ea26-4a8f-9559-e23e579650e8 X-AV-Checked: ClamAV using ClamSMTP Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Guten Tag Zygo Blaxell, am Freitag, 28. Mai 2021 um 21:36 schrieben Sie: > Nothing happens to the snapshots. 'fi defrag' will make new, possibly > compressed (but possibly not compressed) duplicate copies of the data > in the listed files. These copies will use separate storage space from > the snapshots. Thanks for clearing things up, that what's I expected already. > Each individual extent written on the filesystem contains its own > independent copy of compression parameters[...] This brings me to the following in the wiki, not sure if it's worth an additional thread: > There is a simple decision logic: if the first portion of data being > compressed is not smaller than the original, the compression of the > file is disabled[...] https://btrfs.wiki.kernel.org/index.php/Compression#What_happens_to_incompressible_files.3F If (de)compression methods are managed by extents always anway, is the statement in the wiki really true that compression of a whole FILE is disabled if the first portion can't be compressed? Or does the quoted sentence refer to EXTENTS instead of whole FILES instead? "btrfs-compsize" prints the following for one of my directories, which means that at least some parts of the file are compressed, others are not. > Processed 230 files, 754137 regular extents (754137 refs), 3 inline. > Type Perc Disk Usage Uncompressed Referenced > TOTAL 87% 163G 187G 187G > none 100% 130G 130G 130G > lzo 57% 32G 56G 56G So does this really mean that I was simply lucky because "the first portion" of the file could be compressed? If that wouldn't the case, the whole file would be uncompressed even though other parts of the file might be compressed pretty well? Referrring to the FILE in the wiki instead of EXTENTS doesn't make too much sense to me currently. Mit freundlichen Grüßen Thorsten Schöning -- AM-SoFT IT-Service - Bitstore Hameln GmbH i.G. Mitglied der Bitstore Gruppe - Ihr Full-Service-Dienstleister für IT und TK E-Mail: Thorsten.Schoening@AM-SoFT.de Web: http://www.AM-SoFT.de/ Tel: 05151- 9468- 0 Tel: 05151- 9468-55 Fax: 05151- 9468-88 Mobil: 0178-8 9468-04 AM-SoFT IT-Service - Bitstore Hameln GmbH i.G., Brandenburger Str. 7c, 31789 Hameln AG Hannover HRB neu - Geschäftsführer: Janine Galonska Für Rückfragen stehe ich Ihnen sehr gerne zur Verfügung. Mit freundlichen Grüßen Thorsten Schöning Tel: 05151 9468 0 Fax: 05151 9468 88 Mobil: Webseite: https://www.am-soft.de AM-Soft IT-Service - Bitstore Hameln GmbH i.G. ist ein Mitglied der Bitstore Gruppe - Ihr Full-Service-Dienstleister für IT und TK AM-Soft IT-Service - Bitstore Hameln GmbH i.G. 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