From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <d.csapak@proxmox.com> Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 2A8F58A5BA for <pbs-devel@lists.proxmox.com>; Thu, 20 Oct 2022 09:41:32 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 0109D4124 for <pbs-devel@lists.proxmox.com>; Thu, 20 Oct 2022 09:41:02 +0200 (CEST) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS for <pbs-devel@lists.proxmox.com>; Thu, 20 Oct 2022 09:40:59 +0200 (CEST) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 91BFE44AA5 for <pbs-devel@lists.proxmox.com>; Thu, 20 Oct 2022 09:40:59 +0200 (CEST) From: Dominik Csapak <d.csapak@proxmox.com> To: pbs-devel@lists.proxmox.com Date: Thu, 20 Oct 2022 09:40:57 +0200 Message-Id: <20221020074058.717152-5-d.csapak@proxmox.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20221020074058.717152-1-d.csapak@proxmox.com> References: <20221020074058.717152-1-d.csapak@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL 0.068 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: [pbs-devel] [PATCH proxmox-backup v3 4/5] docs: add documentation about the 'sync-level' tuning X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion <pbs-devel.lists.proxmox.com> List-Unsubscribe: <https://lists.proxmox.com/cgi-bin/mailman/options/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=unsubscribe> List-Archive: <http://lists.proxmox.com/pipermail/pbs-devel/> List-Post: <mailto:pbs-devel@lists.proxmox.com> List-Help: <mailto:pbs-devel-request@lists.proxmox.com?subject=help> List-Subscribe: <https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=subscribe> X-List-Received-Date: Thu, 20 Oct 2022 07:41:32 -0000 Signed-off-by: Dominik Csapak <d.csapak@proxmox.com> --- docs/storage.rst | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/docs/storage.rst b/docs/storage.rst index 1909bd84..c4e44c72 100644 --- a/docs/storage.rst +++ b/docs/storage.rst @@ -338,3 +338,39 @@ and only available on the CLI: # proxmox-backup-manager datastore update <storename> --tuning 'chunk-order=none' +* ``sync-level``: Datastore fsync level: + + You can set the level of syncing on the datastore for chunks, which influences + the crash resistance of backups in case of a powerloss or hard shutoff. + There are currently three levels: + + - `none` (default): Does not do any syncing when writing chunks. This is fast + and normally OK, since the kernel eventually flushes writes onto the disk. + The kernel sysctls `dirty_expire_centisecs` and `dirty_writeback_centisecs` + are used to tune that behaviour, while the default is to flush old data + after ~30s. + + - `filesystem` : This triggers a ``syncfs(2)`` after a backup, but before + the task returns `OK`. This way it is ensured that the written backups + are on disk. This is a good balance between speed and consistency. + Note that the underlying storage device still needs to protect itself against + powerloss to flush its internal ephemeral caches to the permanent storage layer. + + - `file` With this mode, a fsync is triggered on every chunk insertion, which + makes sure each and every chunk reaches the disk as soon as possible. While + this reaches the highest level of consistency, for many storages (especially + slower ones) this comes at the cost of speed. For many users the `filesystem` + mode is better suited, but for very fast storages this mode can be OK. + + This can be set with: + +.. code-block:: console + + # proxmox-backup-manager datastore update <storename> --tuning 'sync-level=filesystem' + +If you want to set multiple tuning options simultaneously, you can separate them +with a comma, like this: + +.. code-block:: console + + # proxmox-backup-manager datastore update <storename> --tuning 'sync-level=filesystem,chunk-order=none' -- 2.30.2