sys/sys/sysid.h

   1 /*
   2  * Copyright (c) 2007 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/sys/sys/sysid.h,v 1.1 2007/04/29 01:29:31 dillon Exp $
  35  */
  36
  37 #ifndef _SYS_SYSID_H_
  38 #define _SYS_SYSID_H_
  39
  40 /*
  41  * SYSIDs are 64 bit entities and come in two varieties.  Physical SYSIDs
  42  * are used to efficiently route messages across the mesh, while Logical
  43  * SYSIDs are persistently assigned identifiers representing specific devices
  44  * or specific media or named filesystems.  That is, the logical SYSID
  45  * assigned to a filesystem or ANVIL partition can be stored in that
  46  * filesystem's superblock and allows the filesystem to migrate or
  47  * be multi-homed (have multiple physical SYSIDs representing the same
  48  * logical entity).
  49  *
  50  * Physical SYSIDs can be ever-changing, and any given logical SYSID could
  51  * in fact have multiple physical SYSIDs associated with it.  The mesh is
  52  * self-healing and the combination of the logical and physical sysid
  53  * basically validates the message at the target and determines whether
  54  * the physical SYSID must be recalculated (looked up again) or not.
  55  */
  56
  57 typedef u_int64_t       sysid_t;
  58
  59 #endif