From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:34871) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RjAPJ-00040C-R0 for qemu-devel@nongnu.org; Fri, 06 Jan 2012 09:04:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RjAPI-0002L5-LV for qemu-devel@nongnu.org; Fri, 06 Jan 2012 09:04:33 -0500 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:41550) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RjAPI-0002Js-9c for qemu-devel@nongnu.org; Fri, 06 Jan 2012 09:04:32 -0500 Received: from /spool/local by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 6 Jan 2012 14:04:26 -0000 Received: from d06av11.portsmouth.uk.ibm.com (d06av11.portsmouth.uk.ibm.com [9.149.37.252]) by d06nrmr1707.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q06E3v7g2527442 for ; Fri, 6 Jan 2012 14:03:57 GMT Received: from d06av11.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av11.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q06E3vtu021286 for ; Fri, 6 Jan 2012 07:03:57 -0700 From: Stefan Hajnoczi Date: Fri, 6 Jan 2012 14:01:40 +0000 Message-Id: <1325858501-25741-15-git-send-email-stefanha@linux.vnet.ibm.com> In-Reply-To: <1325858501-25741-1-git-send-email-stefanha@linux.vnet.ibm.com> References: <1325858501-25741-1-git-send-email-stefanha@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH v4 14/15] add doc to describe live block operations List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Marcelo Tosatti , Stefan Hajnoczi , Luiz Capitulino From: Marcelo Tosatti Signed-off-by: Marcelo Tosatti Signed-off-by: Stefan Hajnoczi --- docs/live-block-ops.txt | 58 +++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 58 insertions(+), 0 deletions(-) create mode 100644 docs/live-block-ops.txt diff --git a/docs/live-block-ops.txt b/docs/live-block-ops.txt new file mode 100644 index 0000000..a257087 --- /dev/null +++ b/docs/live-block-ops.txt @@ -0,0 +1,58 @@ +LIVE BLOCK OPERATIONS +===================== + +High level description of live block operations. Note these are not +supported for use with the raw format at the moment. + +Snapshot live merge +=================== + +Given a snapshot chain, described in this document in the following +format: + +[A] -> [B] -> [C] -> [D] + +Where the rightmost object ([D] in the example) described is the current +image which the guest OS has write access to. To the left of it is its base +image, and so on accordingly until the leftmost image, which has no +base. + +The snapshot live merge operation transforms such a chain into a +smaller one with fewer elements, such as this transformation relative +to the first example: + +[A] -> [D] + +Currently only forward merge with target being the active image is +supported, that is, data copy is performed in the right direction with +destination being the rightmost image. + +The operation is implemented in QEMU through image streaming facilities. + +The basic idea is to execute 'block_stream virtio0' while the guest is +running. Progress can be monitored using 'info block-jobs'. When the +streaming operation completes it raises a QMP event. 'block_stream' +copies data from the backing file(s) into the active image. When finished, +it adjusts the backing file pointer. + +The 'base' parameter specifies an image which data need not be streamed from. +This image will be used as the backing file for the active image when the +operation is finished. + +In the example above, the command would be: + +(qemu) block_stream virtio0 A + + +Live block copy +=============== + +To copy an in use image to another destination in the filesystem, one +should create a live snapshot in the desired destination, then stream +into that image. Example: + +(qemu) snapshot_blkdev ide0-hd0 /new-path/disk.img qcow2 + +(qemu) block_stream ide0-hd0 + + -- 1.7.7.3