From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932451Ab3LTMjl (ORCPT ); Fri, 20 Dec 2013 07:39:41 -0500 Received: from mail09.linbit.com ([212.69.161.110]:38632 "EHLO mail09.linbit.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932358Ab3LTMj0 (ORCPT ); Fri, 20 Dec 2013 07:39:26 -0500 From: Philipp Reisner To: linux-kernel@vger.kernel.org, Jens Axboe Cc: drbd-dev@lists.linbit.com Subject: [PATCH 03/26] drbd: Describe the future high-level structure of DRBD Date: Fri, 20 Dec 2013 13:29:00 +0100 Message-Id: <1387542563-6833-4-git-send-email-philipp.reisner@linbit.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1387542563-6833-1-git-send-email-philipp.reisner@linbit.com> References: <1387542563-6833-1-git-send-email-philipp.reisner@linbit.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andreas Gruenbacher The following commits will successively transform DRBD into the structure described here. Signed-off-by: Andreas Gruenbacher Signed-off-by: Philipp Reisner --- Documentation/blockdev/drbd/data-structure-v9.txt | 38 +++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 Documentation/blockdev/drbd/data-structure-v9.txt diff --git a/Documentation/blockdev/drbd/data-structure-v9.txt b/Documentation/blockdev/drbd/data-structure-v9.txt new file mode 100644 index 0000000..1e52a0e --- /dev/null +++ b/Documentation/blockdev/drbd/data-structure-v9.txt @@ -0,0 +1,38 @@ +This describes the in kernel data structure for DRBD-9. Starting with +Linux v3.14 we are reorganizing DRBD to use this data structure. + +Basic Data Structure +==================== + +A node has a number of DRBD resources. Each such resource has a number of +devices (aka volumes) and connections to other nodes ("peer nodes"). Each DRBD +device is represented by a block device locally. + +The DRBD objects are interconnected to form a matrix as depicted below; a +drbd_peer_device object sits at each intersection between a drbd_device and a +drbd_connection: + + /--------------+---------------+.....+---------------\ + | resource | device | | device | + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + +--------------+---------------+.....+---------------+ + : : : : : + : : : : : + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + \--------------+---------------+.....+---------------/ + +In this table, horizontally, devices can be accessed from resources by their +volume number. Likewise, peer_devices can be accessed from connections by +their volume number. Objects in the vertical direction are connected by double +linked lists. There are back pointers from peer_devices to their connections a +devices, and from connections and devices to their resource. + +All resources are in the drbd_resources double-linked list. In addition, all +devices can be accessed by their minor device number via the drbd_devices idr. + +The drbd_resource, drbd_connection, and drbd_device objects are reference +counted. The peer_device objects only serve to establish the links between +devices and connections; their lifetime is determined by the lifetime of the +device and connection which they reference. -- 1.7.9.5