From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) by lore.proxmox.com (Postfix) with ESMTPS id 435031FF16B for ; Thu, 14 Nov 2024 16:16:41 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 80E8934C73; Thu, 14 Nov 2024 16:16:43 +0100 (CET) From: Christian Ebner To: pbs-devel@lists.proxmox.com Date: Thu, 14 Nov 2024 16:15:51 +0100 Message-Id: <20241114151551.407971-2-c.ebner@proxmox.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20241114151551.407971-1-c.ebner@proxmox.com> References: <20241114151551.407971-1-c.ebner@proxmox.com> MIME-Version: 1.0 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.032 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy 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 v3 proxmox-backup 2/2] docs: deduplicate background details for garbage collection X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Proxmox Backup Server development discussion Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: pbs-devel-bounces@lists.proxmox.com Sender: "pbs-devel" Currently, common details regarding garbage collection are documented in the backup client and the maintenance task. Deduplicate this information by moving the details to the background section of the maintenance task and reference that section in the backup client part. Reviewed-by: Gabriel Goller Signed-off-by: Christian Ebner --- changes since version 2: - s/can consider/considers/ - s/safeley/safely/ docs/backup-client.rst | 28 ++++++++++++---------------- docs/maintenance.rst | 38 +++++++++++++++++++++++++++----------- 2 files changed, 39 insertions(+), 27 deletions(-) diff --git a/docs/backup-client.rst b/docs/backup-client.rst index e56e0625b..892be11d9 100644 --- a/docs/backup-client.rst +++ b/docs/backup-client.rst @@ -789,29 +789,25 @@ Garbage Collection ------------------ The ``prune`` command removes only the backup index files, not the data -from the datastore. This task is left to the garbage collection -command. It is recommended to carry out garbage collection on a regular basis. +from the datastore. Deletion of unused backup data from the datastore is done by +:ref:`garbage collection<_maintenance_gc>`. It is therefore recommended to +schedule garbage collection tasks on a regular basis. The working principle of +garbage collection is described in more details in the related :ref:`background +section `. -The garbage collection works in two phases. In the first phase, all -data blocks that are still in use are marked. In the second phase, -unused data blocks are removed. +To start garbage collection from the client side, run the following command: + +.. code-block:: console + + # proxmox-backup-client garbage-collect .. note:: This command needs to read all existing backup index files and touches the complete chunk-store. This can take a long time depending on the number of chunks and the speed of the underlying disks. -.. note:: The garbage collection will only remove chunks that haven't been used - for at least one day (exactly 24h 5m). This grace period is necessary because - chunks in use are marked by touching the chunk which updates the ``atime`` - (access time) property. Filesystems are mounted with the ``relatime`` option - by default. This results in a better performance by only updating the - ``atime`` property if the last access has been at least 24 hours ago. The - downside is that touching a chunk within these 24 hours will not always - update its ``atime`` property. - - Chunks in the grace period will be logged at the end of the garbage - collection task as *Pending removals*. +The progress of the garbage collection will be displayed as shown in the example +below: .. code-block:: console diff --git a/docs/maintenance.rst b/docs/maintenance.rst index 601756246..a64769138 100644 --- a/docs/maintenance.rst +++ b/docs/maintenance.rst @@ -197,6 +197,8 @@ It's recommended to setup a schedule to ensure that unused space is cleaned up periodically. For most setups a weekly schedule provides a good interval to start. +.. _gc_background: + GC Background ^^^^^^^^^^^^^ @@ -222,17 +224,31 @@ datastore or interfering with other backups. The garbage collection (GC) process is performed per datastore and is split into two phases: -- Phase one: Mark - All index files are read, and the access time of the referred chunk files is - updated. - -- Phase two: Sweep - The task iterates over all chunks, checks their file access time, and if it - is older than the cutoff time (i.e., the time when GC started, plus some - headroom for safety and Linux file system behavior), the task knows that the - chunk was neither referred to in any backup index nor part of any currently - running backup that has no index to scan for. As such, the chunk can be - safely deleted. +- Phase one (Mark): + + All index files are read, and the access time (``atime``) of the referenced + chunk files is updated. + +- Phase two (Sweep): + + The task iterates over all chunks and checks their file access time against a + cutoff time. The cutoff time is given by either the oldest backup writer + instance, if present, or 24 hours and 5 minutes after the start of garbage + collection. + + Garbage collection considers chunk files with access time older than the + cutoff time to be neither referenced by any backup snapshot's index, nor part + of any currently running backup job. Therefore, these chunks can safely be + deleted. + + Chunks within the grace period will not be deleted and logged at the end of + the garbage collection task as *Pending removals*. + +.. note:: The grace period for backup chunk removal is not arbitrary, but stems + from the fact that filesystems are typically mounted with the ``relatime`` + option by default. This results in better performance by only updating the + ``atime`` property if a file has been modified since the last access or the + last access has been at least 24 hours ago. Manually Starting GC ^^^^^^^^^^^^^^^^^^^^ -- 2.39.5 _______________________________________________ pbs-devel mailing list pbs-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel