From nobody Mon Feb 9 03:14:24 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of redhat.com designates 170.10.133.124 as permitted sender) client-ip=170.10.133.124; envelope-from=libvir-list-bounces@redhat.com; helo=us-smtp-delivery-124.mimecast.com; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=libvir-list-bounces@redhat.com; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1638543918; cv=none; d=zohomail.com; s=zohoarc; b=Eq+Y0WN8MUBVjfMvp4StHc5+sLNLsCx0xRy2ysACcaB5Pisb3jkwj8O4+dhxNN2l9v6/ksKdfy1hZh5JDOLevo0himQUyFkT5Gm+/7yBNhktswHWLNQOzBbaGgBJh7XRboO/IpQOCddvKrqABT89oops3G85K7X8R7vEC4zssAk= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1638543918; h=Content-Type:Content-Transfer-Encoding:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; 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t=1638543917; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=pgxX9jF4RggdrsV/z00rUcKvprOULNSJvWoVb/iuxdk=; b=crJ8Rtmol76G24ePCylFsld6sMCyePAWOnNlTeyswJx6x68d2ShWTaHhMueK8WarzXLBx5 JzP3c0K/Xxn9060ZjeO3AjmasRgydrN1nMoeID1Lt7VaFtwrRB3fTKLHJkV0nx91N1vTdO S1ZQKDewdVHyd2z5sgZ8ptlbQ95uJFU= X-MC-Unique: _oiUQZftOhmZxQhu9OGoAw-1 From: Peter Krempa To: libvir-list@redhat.com Subject: [PATCH 16/17] docs: migration: Add a paragraph about non-shared storage migration Date: Fri, 3 Dec 2021 16:01:55 +0100 Message-Id: <3dd42bcdd54c7de347a09b92976e755393aa8446.1638543496.git.pkrempa@redhat.com> In-Reply-To: References: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-loop: libvir-list@redhat.com X-BeenThere: libvir-list@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Development discussions about the libvirt library & tools List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: libvir-list-bounces@redhat.com Errors-To: libvir-list-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=libvir-list-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1638543918759100001 Content-Type: text/plain; charset="utf-8" Outline some of the basics and the caveats of the non-shared migration code. Signed-off-by: Peter Krempa --- docs/migration.rst | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/docs/migration.rst b/docs/migration.rst index 0a40600462..247f345f8c 100644 --- a/docs/migration.rst +++ b/docs/migration.rst @@ -446,6 +446,38 @@ SELinux rules and settings of your system. Supported by QEMU driver + +Migration of VMs using non-shared images for disks +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Libvirt by default expects that the disk images which are not explicitly n= etwork +accessed are shared between the hosts by means of a network filesystem or = remote +block storage. + +By default it's expected that they are in the same location, but this can = be +modified by providing an updated domain XML with appropriate paths to the = images +using ``--xml`` argument for ``virsh migrate``. + +In case when one or more of the images are residing on local storage libvi= rt +can migrate them as part of the migration flow. This is enabled using +``--copy-storage-all`` flag for ``virsh migrate``. Additionally +``--migrate-disks`` parameter allows control which disks need to actually = be +migrated. Without the flag all read-write disks are migrated. + +On the destination the images must be either pre-created by the user having +correct format and size or alternatively if the target path resides within= a +libvirt storage pool they will be automatically created. + +In case when the user wishes to migrate only the topmost image from a back= ing +chain of images for each disks ``--copy-storage-inc`` can be used instead.= User +must pre-create the images unconditionally. + +In order to ensure that the migration of disks will not be overwhelmed by a +guest doing a lot of I/O to a local fast storage the +``--copy-storage-synchronous-writes`` flag ensures that newly written data= is +synchronously written to the destination. This may harm I/O performance du= ring +the migration. + .. |Migration native path| image:: migration-native.png :class: diagram .. |Migration tunnel path| image:: migration-tunnel.png --=20 2.31.1