290 lines
6.5 KiB
Text
290 lines
6.5 KiB
Text
.TH AOE 3
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.SH NAME
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aoe \- ATA-over-Ethernet (AoE) interface
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.SH SYNOPSIS
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.nf
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.B bind -a #æ /dev
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.sp 0.3v
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.B /dev/aoe/ctl
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.B /dev/aoe/log
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.BI /dev/aoe/ shelf . slot /config
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.BI /dev/aoe/ shelf . slot /ctl
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.BI /dev/aoe/ shelf . slot /devlink/0
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\&...
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.BI /dev/aoe/ shelf . slot /devlink/ i
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.BI /dev/aoe/ shelf . slot /ident
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\&...
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.fi
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.SH DESCRIPTION
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The AoE (ATA-over-Ethernet) interface serves a three-level
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directory providing control and access to AoE targets.
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The interface provided is primarily intended for low-level
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control of the AoE initiator. See
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.IR sdaoe (3)
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for the standard interface.
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.SS Top-level files
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In order to access AoE targets, one or more Ethernet controllers
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need to be bound to the AoE initiator. By default, the system
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starts with no interfaces bound. For automatic binding of interfaces
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on boot, the
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.B aoeif
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configuration variable is set in
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.IR plan9.ini (8).
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Ethernet interfaces are specified as
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.BI ether n\fR,
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not as
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.BI #l n\fR.
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To bind the first and second Ethernet devices on boot, add
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.IP
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.EX
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aoeif=ether0 ether1
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.EE
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.PP
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To bind
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.B ether1
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to a running system:
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.IP
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.EX
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% echo bind '#l1/ether1' >/dev/aoe/ctl
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.EE
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.PP
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And to unbind it
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.IP
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.EX
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% echo unbind '#l1/ether1' >/dev/aoe/ctl
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.EE
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.PP
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When an interface is unbound, targets depending
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on that interface are removed.
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.PP
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Each local interface is called a
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.IR netlink .
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The mapping of
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AoE targets to netlinks is called a
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.IR devlink .
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Each devlink may
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see multiple interfaces per target.
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For example, if the local
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machine has one Ethernet address bound and the target has
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two interfaces on the same Ethernet segment, this will result
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in one netlink and one devlink with two Ethernet addresses.
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AoE frames are sent in round-robin fashion.
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Each successive
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frame is sent on the next address available on the next available
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devlink (local interface).
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.PP
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Normally the initiator automatically discovers and adds new
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device directories on startup. New devices are not added
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except as new interfaces are bound to the initiator.
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Several messages can be written to
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.B /dev/aoe/ctl
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which alter this behavior:
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.TP
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.BI autodiscover\ toggle
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If toggle is absent,
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the state of
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.B autodiscover
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is toggled. If it is the string
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.BR on ,
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it is turned on. Any other string turns
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.B autodisover
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off.
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This option is not useful after Ethernet devices have been bound.
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.TP
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.BI discover\ shelf.slot
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Attempt to find the named target on all bound interfaces.
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.TP
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.BI remove\ shelf.slot
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The converse of
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.BR discover :
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remove the named target if it exists.
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.TP
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.BI rediscover\ toggle
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Allow or disallow rediscovery.
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This allows for automatic discovery of new targets.
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Unfortunately, it also allows automatic modification
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or loss of existing targets. This option is considered dangerous.
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.br
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.ne 4
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.PP
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Reading
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.B /dev/aoe/ctl
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returns a list of colon-separated lines
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with keywords and their values:
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.TF rediscover
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.PD
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.TP
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.BI debug
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.PD 0
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.TP
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.BI autodiscover
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.TP
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.B rediscover
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Returns the current state of the variable named by the keyword.
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Writing the variable's
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name to the control file toggles the state of that variable.
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.PD
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.TP
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.BI if "n path"
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Path to
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.IR n th
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bound Ethernet device.
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.TP
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.BI if "n ea"
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Ethernet address of this device.
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.TP
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.BI if "n flag"
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A flag of ``Up'' indicates that this interface is available.
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.TP
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.BI if "n lostjumbo"
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Number of consecutive lost jumbograms.
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.TP
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.BI if "n datamtu"
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Incorrect and unused.
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.SS Shelf-and-slot subdirectories
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Once configured, each AoE target is accessed via files in the directory named
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for its shelf and slot. For example, shelf 42, slot 0 would be
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accessed through the path
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.LR /dev/aoe/42.0 .
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The
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.B ident
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file contains the read-only, verbatim result of the identify unit ATA command.
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The
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.B config
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file contains the target's AoE configuration string. Writing to this file
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sets the targets configuration string.
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.PP
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Reading a shelf and slot's
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.B ctl
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file returns a list of colon-separated lines
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with the following keywords and values:
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.TF firmware
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.PD
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.TP
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.B state
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``Up'' or ``down''.
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.TP
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.B nopen
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Number of clients using this target.
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.TP
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.B nout
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Number of outstanding AoE frames.
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.TP
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.B nmaxout
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Maximum number of outstanding frames allowed.
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.TP
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.B nframes
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Maximum number of outstanding frames.
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.I Nframes
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is greater than
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.I nmaxout
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when the initiator is reducing the number of in-flight
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frames due to packet loss. It is assumed that packet
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loss is due to an overwhelmed target and not poor
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network conditions.
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.TP
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.BI maxbcount
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Maximum number of data bytes per AoE frame. Using
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standard frames,
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.B maxbcount
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is 1024 or two sectors.
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AoE ATA headers are 36 bytes.
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.TP
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.B model
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.PD 0
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.TP
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.B serial
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.TP
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.B firmware
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The respective fields from the ATA
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.B identify unit
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command.
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.PD
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.TP
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.B flag
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List of flags useful for debugging. The flag
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.B jumbo
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indicates that jumbo frames are accepted, not that
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they are being used.
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.I Maxbcount
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should be consulted for this purpose.
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.PP
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The
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.B data
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file may be read or written like a normal file
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except that reads and writes to this file are converted to
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AoE commands to the target, so transfers should be 512 or 1024 bytes long
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(or a larger multiple of 512 iff jumbo packets are in use).
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The size of this file is the usable size of the target.
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.PP
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The
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.B devlink
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directory contains one file for each interface the target was
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discovered on. The files are numbers from 0 to
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.I n
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and contain a list of colon-separated lines
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with keywords and their values:
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.TF mintimer
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.PD
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.TP
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.B addr
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A space-separated list of the target's Ethernet addresses visible from
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this interface.
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.TP
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.B npkt
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The number of frames sent on this interface.
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.TP
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.B resent
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The number of frames re-sent. Frames are re-sent
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when they have been outstanding twice the RTT average.
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.TP
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.B flag
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``Up'' when the netlink is up.
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.TP
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.B rttavg
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.PD 0
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.TP
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.B mintimer
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Minimum timer and RTT average as per
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.IR "Congestion Avoidance and Control" .
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.PD
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.TP
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.B nl path
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Path of the Ethernet device.
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.TP
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.B nl ea
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Ethernet address of the local Ethernet device.
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.TP
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.B nl flag
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``Up'' if the local interface is up.
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.TP
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.B nl lostjumbo
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Number of consecutive jumbograms lost.
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.TP
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.B nl datamtu
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Unused.
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.PP
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.SH SOURCE
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.B /sys/src/9/port/devaoe.c
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.SH SEE ALSO
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.\" .IR cec (1),
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.\" .IR vblade (1),
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.IR sd (3),
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.IR sdaoe (3),
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.IR vblade (8),
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.IR snoopy (8)
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.br
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.BR http://www.coraid.com/documents/AoEr10.txt
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.br
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Van Jacobson and Michael J. Karels,
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.IR "``Congestion Avoidance and Control''" ,
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ACM Computer Communication Review;
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Proceedings of the Sigcomm '88 Symposium in Stanford, CA, August, 1988.
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.SH BUGS
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There is no
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.B raw
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file for executing arbitrary commands.
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.PP
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This is a fairly primitive interface;
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.IR sdaoe (3)
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is usually more suitable.
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