AOE(3) AOE(3) NAME aoe - ATA-over-Ethernet (AoE) interface SYNOPSIS bind -a #æ /dev 9 /dev/aoe/ctl /dev/aoe/log /dev/aoe/shelf.slot/config /dev/aoe/shelf.slot/ctl /dev/aoe/shelf.slot/devlink/0 ... /dev/aoe/shelf.slot/devlink/i /dev/aoe/shelf.slot/ident ... DESCRIPTION The AoE (ATA-over-Ethernet) interface serves a three-level directory providing control and access to AoE targets. The interface provided is primarily intended for low-level con- trol of the AoE initiator. See sdaoe(3) for the standard interface. Top-level files In order to access AoE targets, one or more Ethernet con- trollers need to be bound to the AoE initiator. By default, the system starts with no interfaces bound. For automatic binding of interfaces on boot, the aoeif configuration vari- able is set in plan9.ini(8). Ethernet interfaces are speci- fied as ethern, not as #ln. To bind the first and second Ethernet devices on boot, add aoeif=ether0 ether1 To bind ether1 to a running system: % echo bind '#l1/ether1' >/dev/aoe/ctl And to unbind it % echo unbind '#l1/ether1' >/dev/aoe/ctl When an interface is unbound, targets depending on that interface are removed. Each local interface is called a netlink. The mapping of AoE targets to netlinks is called a devlink. Each devlink may see multiple interfaces per target. For example, if the local machine has one Ethernet address bound and the target has two interfaces on the same Ethernet segment, this will result in one netlink and one devlink with two Ethernet 9 AOE(3) AOE(3) addresses. AoE frames are sent in round-robin fashion. Each successive frame is sent on the next address available on the next available devlink (local interface). Normally the initiator automatically discovers and adds new device directories on startup. New devices are not added except as new interfaces are bound to the initiator. Sev- eral messages can be written to /dev/aoe/ctl which alter this behavior: autodiscover toggle If toggle is absent, the state of autodiscover is tog- gled. If it is the string on, it is turned on. Any other string turns autodisover off. This option is not useful after Ethernet devices have been bound. discover shelf.slot Attempt to find the named target on all bound inter- faces. remove shelf.slot The converse of discover: remove the named target if it exists. rediscover toggle Allow or disallow rediscovery. This allows for auto- matic discovery of new targets. Unfortunately, it also allows automatic modification or loss of existing tar- gets. This option is considered dangerous. Reading /dev/aoe/ctl returns a list of colon-separated lines with keywords and their values: debug autodiscover rediscover Returns the current state of the variable named by the keyword. Writing the variable's name to the control file toggles the state of that vari- able. ifn path Path to nth bound Ethernet device. ifn ea Ethernet address of this device. ifn flag A flag of ``Up'' indicates that this interface is available. ifn lostjumbo Number of consecutive lost jumbograms. ifn datamtu Incorrect and unused. AOE(3) AOE(3) Shelf-and-slot subdirectories Once configured, each AoE target is accessed via files in the directory named for its shelf and slot. For example, shelf 42, slot 0 would be accessed through the path `/dev/aoe/42.0'. The ident file contains the read-only, verbatim result of the identify unit ATA command. The config file contains the target's AoE configuration string. Writing to this file sets the targets configuration string. Reading a shelf and slot's ctl file returns a list of colon-separated lines with the following keywords and val- ues: state ``Up'' or ``down''. nopen Number of clients using this target. nout Number of outstanding AoE frames. nmaxout Maximum number of outstanding frames allowed. nframes Maximum number of outstanding frames. Nframes is greater than nmaxout when the initiator is reduc- ing the number of in-flight frames due to packet loss. It is assumed that packet loss is due to an overwhelmed target and not poor network condi- tions. maxbcount Maximum number of data bytes per AoE frame. Using standard frames, maxbcount is 1024 or two sectors. AoE ATA headers are 36 bytes. model serial firmware The respective fields from the ATA identify unit command. flag List of flags useful for debugging. The flag jumbo indicates that jumbo frames are accepted, not that they are being used. Maxbcount should be consulted for this purpose. The data file may be read or written like a normal file except that reads and writes to this file are converted to AoE commands to the target, so transfers should be 512 or 1024 bytes long (or a larger multiple of 512 iff jumbo pack- ets are in use). The size of this file is the usable size of the target. The devlink directory contains one file for each interface the target was discovered on. The files are numbers from 0 AOE(3) AOE(3) to n and contain a list of colon-separated lines with key- words and their values: addr A space-separated list of the target's Ethernet addresses visible from this interface. npkt The number of frames sent on this interface. resent The number of frames re-sent. Frames are re-sent when they have been outstanding twice the RTT average. flag ``Up'' when the netlink is up. rttavg mintimer Minimum timer and RTT average as per Congestion Avoidance and Control. nl path Path of the Ethernet device. nl ea Ethernet address of the local Ethernet device. nl flag ``Up'' if the local interface is up. nl lostjumbo Number of consecutive jumbograms lost. nl datamtu Unused. SOURCE /sys/src/9/port/devaoe.c SEE ALSO sd(3), sdaoe(3), vblade(8), snoopy(8) http://www.coraid.com/documents/AoEr10.txt Van Jacobson and Michael J. Karels, ``Congestion Avoidance and Control'', ACM Computer Communication Review; Proceed- ings of the Sigcomm '88 Symposium in Stanford, CA, August, 1988. BUGS There is no raw file for executing arbitrary commands. This is a fairly primitive interface; sdaoe(3) is usually more suitable.