From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 5DBBC90D72 for ; Thu, 25 Jan 2024 15:41:56 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 370ED1B975 for ; Thu, 25 Jan 2024 15:41:56 +0100 (CET) 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 ; Thu, 25 Jan 2024 15:41:55 +0100 (CET) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 0EB29492AC for ; Thu, 25 Jan 2024 15:41:55 +0100 (CET) From: Fiona Ebner To: pve-devel@lists.proxmox.com Date: Thu, 25 Jan 2024 15:41:49 +0100 Message-Id: <20240125144149.216064-14-f.ebner@proxmox.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240125144149.216064-1-f.ebner@proxmox.com> References: <20240125144149.216064-1-f.ebner@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL -0.074 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 T_SCC_BODY_TEXT_LINE -0.01 - Subject: [pve-devel] [RFC docs 13/13] vzdump: add section about backup fleecing X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 25 Jan 2024 14:41:56 -0000 Signed-off-by: Fiona Ebner --- vzdump.adoc | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/vzdump.adoc b/vzdump.adoc index 24a3e80..eb67141 100644 --- a/vzdump.adoc +++ b/vzdump.adoc @@ -136,6 +136,34 @@ not included in backups. For volume mount points you can set the *Backup* option to include the mount point in the backup. Device and bind mounts are never backed up as their content is managed outside the {pve} storage library. +VM Backup Fleecing +~~~~~~~~~~~~~~~~~~ + +WARNING: Backup fleecing is still being worked on (also in upstream QEMU) and is +currently only a technology preview. + +When a backup for a VM is started, QEMU will install a "copy-before-write" +filter in its block layer. This filter ensures that upon new guest writes, old +data still needed for the backup is sent to the backup target first. The guest +write blocks until this operation is finished so guest IO to not-yet-backed-up +sectors will be limited by the speed of the backup target. + +With backup fleecing, such old data is cached in a fleecing image rather than +sent directly to the backup target. This can help guest IO performance and even +prevent hangs in certain scenarios, at the cost of requiring more storage space. +Use e.g. `vzdump 123 --fleecing enabled=1,storage=local-zfs` to enable backup +fleecing, with fleecing images created on the storage `local-zfs`. If no storage +is specified, the fleecing image will be created on the same storage as the +original image. + +WARNING: Theoretically, the fleecing image can grow to the same size as the +original image, e.g. if the guest re-writes a whole disk while the backup is +busy with another disk. + +Parts of the fleecing image that have been backed up will be discarded to try +and keep the space usage low. + + Backup File Names ----------------- -- 2.39.2