harvey/sys/man/3/aoe

.TH AOE 3
.SH NAME
aoe \- ATA-over-Ethernet (AoE) interface
.SH SYNOPSIS
.nf
.B bind -a #æ /dev
.sp 0.3v
.B /dev/aoe/ctl
.B /dev/aoe/log
.BI /dev/aoe/ shelf . slot /config
.BI /dev/aoe/ shelf . slot /ctl
.BI /dev/aoe/ shelf . slot /devlink/0
\&...
.BI /dev/aoe/ shelf . slot /devlink/ i
.BI /dev/aoe/ shelf . slot /ident
\&...
.fi
.SH 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
control of the AoE initiator.  See
.IR sdaoe (3)
for the standard interface.
.SS Top-level files
In order to access AoE targets, one or more Ethernet controllers
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
.B aoeif
configuration variable is set in
.IR plan9.ini (8).
Ethernet interfaces are specified as
.BI ether n\fR,
not as
.BI #l n\fR.
To bind the first and second Ethernet devices on boot, add
.IP
.EX
aoeif=ether0 ether1
.EE
.PP
To bind
.B ether1
to a running system:
.IP
.EX
% echo bind '#l1/ether1' >/dev/aoe/ctl
.EE
.PP
And to unbind it
.IP
.EX
% echo unbind '#l1/ether1' >/dev/aoe/ctl
.EE
.PP
When an interface is unbound, targets depending
on that interface are removed.
.PP
Each local interface is called a
.IR netlink .
The mapping of
AoE targets to netlinks is called a
.IR 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 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).
.PP
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.
Several messages can be written to
.B /dev/aoe/ctl
which alter this behavior:
.TP
.BI autodiscover\  toggle
If toggle is absent,
the state of
.B autodiscover
is toggled.  If it is the string
.BR on ,
it is turned on.  Any other string turns
.B autodisover
off.
This option is not useful after Ethernet devices have been bound.
.TP
.BI discover\  shelf.slot
Attempt to find the named target on all bound interfaces.
.TP
.BI remove\  shelf.slot
The converse of
.BR discover :
remove the named target if it exists.
.TP
.BI rediscover\  toggle
Allow or disallow rediscovery.
This allows for automatic discovery of new targets.
Unfortunately, it also allows automatic modification
or loss of existing targets.  This option is considered dangerous.
.br
.ne 4
.PP
Reading
.B /dev/aoe/ctl
returns a list of colon-separated lines
with keywords and their values:
.TF rediscover
.PD
.TP
.BI debug
.PD 0
.TP
.BI autodiscover
.TP
.B 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 variable.
.PD
.TP
.BI if "n path"
Path to
.IR n th
bound Ethernet device.
.TP
.BI if "n ea"
Ethernet address of this device.
.TP
.BI if "n flag"
A flag of ``Up'' indicates that this interface is available.
.TP
.BI if "n lostjumbo"
Number of consecutive lost jumbograms.
.TP
.BI if "n datamtu"
Incorrect and unused.
.SS "Target 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
.LR /dev/aoe/42.0 .
The
.B ident
file contains the read-only, verbatim result of the identify unit ATA command.
The
.B config
file contains the target's AoE configuration string.  Writing to this file
sets the targets configuration string.
.PP
Reading a target's
.B ctl
file returns a list of colon-separated lines
with the following keywords and values:
.TF firmware
.PD
.TP
.B state
``Up'' or ``down''.
.TP
.B nopen
Number of clients using this target.
.TP
.B nout
Number of outstanding AoE frames.
.TP
.B nmaxout
Maximum number of outstanding frames allowed.
.TP
.B nframes
Maximum number of outstanding frames.
.I Nframes
is greater than
.I nmaxout
when the initiator is reducing 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 conditions.
.TP
.BI maxbcount
Maximum number of data bytes per AoE frame.  Using
standard frames,
.B maxbcount
is 1024 or two sectors.
AoE ATA headers are 36 bytes.
.TP
.B model
.PD 0
.TP
.B serial
.TP
.B firmware
The respective fields from the ATA
.B identify unit
command.
.PD
.TP
.B flag
List of flags useful for debugging.  The flag
.B jumbo
indicates that jumbo frames are accepted, not that
they are being used.
.I Maxbcount
should be consulted for this purpose.
.PP
Writing to the
.B ctl
file, the following commands may be issued:
.TF identify
.PD
.TP
.B failio
fail outstanding i/o.
.TP
.B identify
send an ata
.L "identify device"
command to the target.
.TP
.BI maxbno " n"
set the maximum number of block sent per
packet.
.TP
.BI mtu  " n"
set the maximum number of bytes (including
header) sent per packet.
.TP
.B nofail
never fail this target.  This is useful if your
root device is on this target.
.TP
.BI setsize " n"
with no arguments, reset the device size to
the size claimed.  Otherwise, assume the
device is the given size.
.PP
The
.B 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 packets are in use).
The size of this file is the usable size of the target.
.PP
The
.B devlink
directory contains one file for each interface the target was
discovered on.  The files are numbers from 0 to
.I n
and contain a list of colon-separated lines
with keywords and their values:
.TF mintimer
.PD
.TP
.B addr
A space-separated list of the target's Ethernet addresses visible from
this interface.
.TP
.B npkt
The number of frames sent on this interface.
.TP
.B resent
The number of frames re-sent.  Frames are re-sent
when they have been outstanding twice the RTT average.
.TP
.B flag
``Up'' when the netlink is up.
.TP
.B rttavg
.PD 0
.TP
.B mintimer
Minimum timer and RTT average as per
.IR "Congestion Avoidance and Control" .
.PD
.TP
.B nl path
Path of the Ethernet device.
.TP
.B nl ea
Ethernet address of the local Ethernet device.
.TP
.B nl flag
``Up'' if the local interface is up.
.TP
.B nl lostjumbo
Number of consecutive jumbograms lost.
.TP
.B nl datamtu
Unused.
.PP
.SH SOURCE
.B /sys/src/9/port/devaoe.c
.SH SEE ALSO
.\" .IR cec (8),
.\" .IR vblade (8),
.IR sd (3),
.IR sdaoe (3),
.IR aoesrv (8),
.IR snoopy (8)
.br
.BR http://support.coraid.com/documents/AoEr11.txt
.br
Van Jacobson and Michael J. Karels,
.IR "``Congestion Avoidance and Control''" ,
ACM Computer Communication Review;
Proceedings of the Sigcomm '88 Symposium in Stanford, CA, August, 1988.
.SH BUGS
There is no
.B raw
file for executing arbitrary commands.
.PP
This is a fairly primitive interface;
.IR sdaoe (3)
is usually more suitable.