From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51952) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eTNGk-0006E9-KJ for qemu-devel@nongnu.org; Mon, 25 Dec 2017 02:33:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eTNGi-0001Xm-16 for qemu-devel@nongnu.org; Mon, 25 Dec 2017 02:33:54 -0500 Received: from mga01.intel.com ([192.55.52.88]:27716) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eTNGh-0001W7-Od for qemu-devel@nongnu.org; Mon, 25 Dec 2017 02:33:51 -0500 Message-ID: <1514187226.13662.28.camel@intel.com> From: He Junyan Date: Mon, 25 Dec 2017 15:33:46 +0800 Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] Some question about savem/qcow2 incremental snapshot List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org hi all: I am now focusing on snapshot optimization for Intel NVDimm kind memory. Different from the normal memory, the NVDimm may be 128G, 256G or even more for just one guest, and its speed is slower than the normal memory. So sometimes it may take several minutes to complete just one snapshot saving. Even with compression enabled, the snapshot point may consume more than 30G disk space.  We decide to add incremental kind snapshot saving to resolve this. Just store difference between snapshot points to save time and disk space. But the current snapshot/save_vm framework seems not to support this. We need to add snapshot dependency and extra operations when we LOAD and DELETE the snapshot point. Is that possible to modify the savevm framework and add some incremental snapshot support to QCOW2 format? Thanks