From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id 9EC571FF13B for ; Wed, 22 Apr 2026 10:40:59 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 7E7A7FDB4; Wed, 22 Apr 2026 10:40:59 +0200 (CEST) Message-ID: <84cfe249-23bf-4498-90e1-90b44dd944b2@proxmox.com> Date: Wed, 22 Apr 2026 10:40:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH proxmox-backup v7 2/9] datastore: add move-group To: Hannes Laimer , pbs-devel@lists.proxmox.com References: <20260416171830.266553-1-h.laimer@proxmox.com> <20260416171830.266553-3-h.laimer@proxmox.com> Content-Language: en-US, de-DE From: Christian Ebner In-Reply-To: <20260416171830.266553-3-h.laimer@proxmox.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1776847168621 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.071 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 Message-ID-Hash: CNALXMAF2EYMW3XM6VSQSH57GXOHHPQY X-Message-ID-Hash: CNALXMAF2EYMW3XM6VSQSH57GXOHHPQY X-MailFrom: c.ebner@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox Backup Server development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 4/16/26 7:18 PM, Hannes Laimer wrote: > Add support for moving a single backup group to a different namespace > within the same datastore. > > For the filesystem backend each snapshot directory is renamed > individually. For S3 all objects are copied to the target prefix > before deleting the source, per snapshot. > > Exclusive locks on the group and all its snapshots are acquired > before the move to ensure no concurrent operations are active. > Snapshots are locked and moved in batches to avoid exhausting file > descriptors on groups with many snapshots. Unless I overlook it, there currently is still one major issue which can lead to data loss with this: Garbage collection uses the Datastore's list_index_files() method to collect all index files at the start of phase 1. This is to know which chunks need atime updates to mark them as in use. Snapshots which disappear in the mean time can be ignored, as the chunks may then no longer be in use. Snapshots created in the mean time are safe, as there it is the cutoff time protecting newly written chunks which are not referenced by any of the index files which are now not in the list. But if the move happens after GC started and collected the index files, but before reaching that index files. the moved index file still might reference chunks which are in-use, but now never get an atime update. Locking unfortunately does not protect against this. So if there is an ongoing garbage collection phase 1, there is the need for some mechanism to re-inject the index files in the list of indices and therefore chunks to process. This might require to write the moved indices to a file, so they can be read and processed at the end of GC phase 1 even if GC is running in a different process. And it requires to flock that file and wait for it to become available before continuing. > > If the target group already exists and merging is enabled, the > individual snapshots are moved into the existing target group > provided both groups have the same owner and the source snapshots > are strictly newer than the target snapshots. > > Signed-off-by: Hannes Laimer > --- [..]