aoe.rst (6004B)
1Introduction 2============ 3 4ATA over Ethernet is a network protocol that provides simple access to 5block storage on the LAN. 6 7 http://support.coraid.com/documents/AoEr11.txt 8 9The EtherDrive (R) HOWTO for 2.6 and 3.x kernels is found at ... 10 11 http://support.coraid.com/support/linux/EtherDrive-2.6-HOWTO.html 12 13It has many tips and hints! Please see, especially, recommended 14tunings for virtual memory: 15 16 http://support.coraid.com/support/linux/EtherDrive-2.6-HOWTO-5.html#ss5.19 17 18The aoetools are userland programs that are designed to work with this 19driver. The aoetools are on sourceforge. 20 21 http://aoetools.sourceforge.net/ 22 23The scripts in this Documentation/admin-guide/aoe directory are intended to 24document the use of the driver and are not necessary if you install 25the aoetools. 26 27 28Creating Device Nodes 29===================== 30 31 Users of udev should find the block device nodes created 32 automatically, but to create all the necessary device nodes, use the 33 udev configuration rules provided in udev.txt (in this directory). 34 35 There is a udev-install.sh script that shows how to install these 36 rules on your system. 37 38 There is also an autoload script that shows how to edit 39 /etc/modprobe.d/aoe.conf to ensure that the aoe module is loaded when 40 necessary. Preloading the aoe module is preferable to autoloading, 41 however, because AoE discovery takes a few seconds. It can be 42 confusing when an AoE device is not present the first time the a 43 command is run but appears a second later. 44 45Using Device Nodes 46================== 47 48 "cat /dev/etherd/err" blocks, waiting for error diagnostic output, 49 like any retransmitted packets. 50 51 "echo eth2 eth4 > /dev/etherd/interfaces" tells the aoe driver to 52 limit ATA over Ethernet traffic to eth2 and eth4. AoE traffic from 53 untrusted networks should be ignored as a matter of security. See 54 also the aoe_iflist driver option described below. 55 56 "echo > /dev/etherd/discover" tells the driver to find out what AoE 57 devices are available. 58 59 In the future these character devices may disappear and be replaced 60 by sysfs counterparts. Using the commands in aoetools insulates 61 users from these implementation details. 62 63 The block devices are named like this:: 64 65 e{shelf}.{slot} 66 e{shelf}.{slot}p{part} 67 68 ... so that "e0.2" is the third blade from the left (slot 2) in the 69 first shelf (shelf address zero). That's the whole disk. The first 70 partition on that disk would be "e0.2p1". 71 72Using sysfs 73=========== 74 75 Each aoe block device in /sys/block has the extra attributes of 76 state, mac, and netif. The state attribute is "up" when the device 77 is ready for I/O and "down" if detected but unusable. The 78 "down,closewait" state shows that the device is still open and 79 cannot come up again until it has been closed. 80 81 The mac attribute is the ethernet address of the remote AoE device. 82 The netif attribute is the network interface on the localhost 83 through which we are communicating with the remote AoE device. 84 85 There is a script in this directory that formats this information in 86 a convenient way. Users with aoetools should use the aoe-stat 87 command:: 88 89 root@makki root# sh Documentation/admin-guide/aoe/status.sh 90 e10.0 eth3 up 91 e10.1 eth3 up 92 e10.2 eth3 up 93 e10.3 eth3 up 94 e10.4 eth3 up 95 e10.5 eth3 up 96 e10.6 eth3 up 97 e10.7 eth3 up 98 e10.8 eth3 up 99 e10.9 eth3 up 100 e4.0 eth1 up 101 e4.1 eth1 up 102 e4.2 eth1 up 103 e4.3 eth1 up 104 e4.4 eth1 up 105 e4.5 eth1 up 106 e4.6 eth1 up 107 e4.7 eth1 up 108 e4.8 eth1 up 109 e4.9 eth1 up 110 111 Use /sys/module/aoe/parameters/aoe_iflist (or better, the driver 112 option discussed below) instead of /dev/etherd/interfaces to limit 113 AoE traffic to the network interfaces in the given 114 whitespace-separated list. Unlike the old character device, the 115 sysfs entry can be read from as well as written to. 116 117 It's helpful to trigger discovery after setting the list of allowed 118 interfaces. The aoetools package provides an aoe-discover script 119 for this purpose. You can also directly use the 120 /dev/etherd/discover special file described above. 121 122Driver Options 123============== 124 125 There is a boot option for the built-in aoe driver and a 126 corresponding module parameter, aoe_iflist. Without this option, 127 all network interfaces may be used for ATA over Ethernet. Here is a 128 usage example for the module parameter:: 129 130 modprobe aoe_iflist="eth1 eth3" 131 132 The aoe_deadsecs module parameter determines the maximum number of 133 seconds that the driver will wait for an AoE device to provide a 134 response to an AoE command. After aoe_deadsecs seconds have 135 elapsed, the AoE device will be marked as "down". A value of zero 136 is supported for testing purposes and makes the aoe driver keep 137 trying AoE commands forever. 138 139 The aoe_maxout module parameter has a default of 128. This is the 140 maximum number of unresponded packets that will be sent to an AoE 141 target at one time. 142 143 The aoe_dyndevs module parameter defaults to 1, meaning that the 144 driver will assign a block device minor number to a discovered AoE 145 target based on the order of its discovery. With dynamic minor 146 device numbers in use, a greater range of AoE shelf and slot 147 addresses can be supported. Users with udev will never have to 148 think about minor numbers. Using aoe_dyndevs=0 allows device nodes 149 to be pre-created using a static minor-number scheme with the 150 aoe-mkshelf script in the aoetools.