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    1 ATA over Ethernet is a network protocol that provides simple access to
    2 block storage on the LAN.
    3 
    4   http://support.coraid.com/documents/AoEr10.txt
    5 
    6 The EtherDrive (R) HOWTO for users of 2.6 kernels is found at ...
    7 
    8   http://support.coraid.com/support/linux/EtherDrive-2.6-HOWTO.html
    9 
   10   It has many tips and hints!
   11 
   12 The aoetools are userland programs that are designed to work with this
   13 driver.  The aoetools are on sourceforge.
   14 
   15   http://aoetools.sourceforge.net/
   16 
   17 The scripts in this Documentation/aoe directory are intended to
   18 document the use of the driver and are not necessary if you install
   19 the aoetools.
   20 
   21 
   22 CREATING DEVICE NODES
   23 
   24   Users of udev should find the block device nodes created
   25   automatically, but to create all the necessary device nodes, use the
   26   udev configuration rules provided in udev.txt (in this directory).
   27 
   28   There is a udev-install.sh script that shows how to install these
   29   rules on your system.
   30 
   31   There is also an autoload script that shows how to edit
   32   /etc/modprobe.conf to ensure that the aoe module is loaded when
   33   necessary.  Preloading the aoe module is preferable to autoloading,
   34   however, because AoE discovery takes a few seconds.  It can be
   35   confusing when an AoE device is not present the first time the a
   36   command is run but appears a second later.
   37 
   38 USING DEVICE NODES
   39 
   40   "cat /dev/etherd/err" blocks, waiting for error diagnostic output,
   41   like any retransmitted packets.
   42 
   43   "echo eth2 eth4 > /dev/etherd/interfaces" tells the aoe driver to
   44   limit ATA over Ethernet traffic to eth2 and eth4.  AoE traffic from
   45   untrusted networks should be ignored as a matter of security.  See
   46   also the aoe_iflist driver option described below.
   47 
   48   "echo > /dev/etherd/discover" tells the driver to find out what AoE
   49   devices are available.
   50 
   51   In the future these character devices may disappear and be replaced
   52   by sysfs counterparts.  Using the commands in aoetools insulates
   53   users from these implementation details.
   54 
   55   The block devices are named like this:
   56 
   57 	e{shelf}.{slot}
   58 	e{shelf}.{slot}p{part}
   59 
   60   ... so that "e0.2" is the third blade from the left (slot 2) in the
   61   first shelf (shelf address zero).  That's the whole disk.  The first
   62   partition on that disk would be "e0.2p1".
   63 
   64 USING SYSFS
   65 
   66   Each aoe block device in /sys/block has the extra attributes of
   67   state, mac, and netif.  The state attribute is "up" when the device
   68   is ready for I/O and "down" if detected but unusable.  The
   69   "down,closewait" state shows that the device is still open and
   70   cannot come up again until it has been closed.
   71 
   72   The mac attribute is the ethernet address of the remote AoE device.
   73   The netif attribute is the network interface on the localhost
   74   through which we are communicating with the remote AoE device.
   75 
   76   There is a script in this directory that formats this information in
   77   a convenient way.  Users with aoetools should use the aoe-stat
   78   command.
   79 
   80   root@makki root# sh Documentation/aoe/status.sh 
   81      e10.0            eth3              up
   82      e10.1            eth3              up
   83      e10.2            eth3              up
   84      e10.3            eth3              up
   85      e10.4            eth3              up
   86      e10.5            eth3              up
   87      e10.6            eth3              up
   88      e10.7            eth3              up
   89      e10.8            eth3              up
   90      e10.9            eth3              up
   91       e4.0            eth1              up
   92       e4.1            eth1              up
   93       e4.2            eth1              up
   94       e4.3            eth1              up
   95       e4.4            eth1              up
   96       e4.5            eth1              up
   97       e4.6            eth1              up
   98       e4.7            eth1              up
   99       e4.8            eth1              up
  100       e4.9            eth1              up
  101 
  102   Use /sys/module/aoe/parameters/aoe_iflist (or better, the driver
  103   option discussed below) instead of /dev/etherd/interfaces to limit
  104   AoE traffic to the network interfaces in the given
  105   whitespace-separated list.  Unlike the old character device, the
  106   sysfs entry can be read from as well as written to.
  107 
  108   It's helpful to trigger discovery after setting the list of allowed
  109   interfaces.  The aoetools package provides an aoe-discover script
  110   for this purpose.  You can also directly use the
  111   /dev/etherd/discover special file described above.
  112 
  113 DRIVER OPTIONS
  114 
  115   There is a boot option for the built-in aoe driver and a
  116   corresponding module parameter, aoe_iflist.  Without this option,
  117   all network interfaces may be used for ATA over Ethernet.  Here is a
  118   usage example for the module parameter.
  119 
  120     modprobe aoe_iflist="eth1 eth3"
  121 
  122   The aoe_deadsecs module parameter determines the maximum number of
  123   seconds that the driver will wait for an AoE device to provide a
  124   response to an AoE command.  After aoe_deadsecs seconds have
  125   elapsed, the AoE device will be marked as "down".  A value of zero
  126   is supported for testing purposes and makes the aoe driver keep
  127   trying AoE commands forever.
  128 
  129   The aoe_maxout module parameter has a default of 128.  This is the
  130   maximum number of unresponded packets that will be sent to an AoE
  131   target at one time.
  132 
  133   The aoe_dyndevs module parameter defaults to 1, meaning that the
  134   driver will assign a block device minor number to a discovered AoE
  135   target based on the order of its discovery.  With dynamic minor
  136   device numbers in use, a greater range of AoE shelf and slot
  137   addresses can be supported.  Users with udev will never have to
  138   think about minor numbers.  Using aoe_dyndevs=0 allows device nodes
  139   to be pre-created using a static minor-number scheme with the
  140   aoe-mkshelf script in the aoetools.