ietd.conf.5

Ubuntu公司提供免费的iSCSI Target

.\" Process this file with
.\" groff -man -Tascii ietd.conf.5
.\" 
.TH "IETD.CONF" "5" "27 July 2005" "A. Lehmann, M. Zhang and A. Redlich" "File formats"
.SH "NAME"
/etc/ietd.conf \- configuration for iSCSI Enterprise Target Daemon
.SH "SYNOPSIS"
/etc/ietd.conf
.SH "DESCRIPTION"
/etc/ietd.conf contains configuration information for the
.B ietd (8)
command. This is the place, where you configure your iSCSI targets and daemon defaults.
.P
Only lines starting with `#' are ignored. Putting '#' in the middle of a line is disallowed. A line may be extended across multiple lines by making the last character a backslash.
.P
The "Yes" and "No" for parameter values are case sensitive. The parameter names are case insensitive.
.P
The file consists of a global part and zero or more "Target" stanzas. Everything until the first target definition belongs to the global configuration. 

Here is an example:

IncomingUser joe secret
.br 
OutgoingUser jack secret2

Target iqn.2001\-04.com.example:storage.disk2.sys1.xyz
    IncomingUser jim othersecret
    OutgoingUser james yetanothersecret
    Lun 0 Path=/dev/sdc,Type=fileio
    Lun 1 Sectors=10000,Type=nullio
    Alias Test
    HeaderDigest None
    DataDigest None
    MaxConnections 1
    InitialR2T Yes
    ImmediateData No
    MaxRecvDataSegmentLength 8192
    MaxXmitDataSegmentLength 8192
    MaxBurstLength 262144
    FirstBurstLength 65536
    DefaultTime2Wait 2
    DefaultTime2Retain 20
    MaxOutstandingR2T 8
    DataPDUInOrder Yes
    DataSequenceInOrder Yes
    ErrorRecoveryLevel 0
.P
Stanzas start with the word "Target" and the target name. This name must be a globally unique name, as defined by the iSCSI standard : the "iSCSI Qualified Name". The daemon brings the targets up in the order listed.
.SH "GLOBAL OPTIONS"
Global Options are case sensitive.
.TP 
.B [IncomingUser <username> <password>]
The 
.I <username>
and 
.I <password>
used during discovery sessions to authenticate iSCSI initiators. Several of those can be specified for discovery. If no
.B IncomingUser
is specified, any initiator is allowed to open a discovery session.
.RS
HINT: RFC 3720 requires
.I <password>
to be 12 characters long. This is enforced e.g. by MS Initiator.
.RE
.TP 
.B [OutgoingUser <username> <password>]
The 
.I <username>
and 
.I <password>
used during discovery sessions to authenticate the target to initiators. Only one outgoing 
.I <username>/<password>
combination may be specified.
.RS
HINT: RFC 3720 requires
.I <password>
to be 12 characters long. This is enforced e.g. by MS Initiator.
.RE
.TP 
.B Target iqn.<yyyy\-mm>.<tld.domain.some.host>[:<identifier>]
A target definition and the target name. The targets name (the
.B iSCSI Qualified Name
) must be a globally unique name (as defined by the iSCSI standard) and has to start with
.I iqn
followed by a single dot. The EUI\-64 form is not supported. 
.I <yyyy\-mm>
is the date (year and month) at which the domain is valid. This has to be followed by a single dot and the reversed domain name.
The optional 
.I <identifier>
\- which is freely selectable \- has to be separated by a single colon. For further details please check the iSCSI spec.

Here is an example:

Target iqn.2004\-07.com.example.host:storage.disk2.sys1.xyz
.SH "TARGET OPTIONS"
Target options are also case sensitive.
.TP 
.B [IncomingUser <username> <password>]
The
.I <username>
and
.I <password>
used to authenticate the iSCSI initiators to this target. It may be different from the username and password in section GLOBAL OPTIONS, which is used for discovery. If you omit the
.B IncomingUser
Option, connections are allowed without authentication. A
.I <password>
has to be provided, if there is a 
.I <username>
given. Specifying several different
.B IncomingUser
accounts is supported.
.TP 
.B [OutgoingUser <username> <password>]
The
.I <username>
and
.I <password>
used to authenticate this iSCSI target to initiators. Only one
.B 
OutgoingUser
per target is supported. It may be different from the username and password in section GLOBAL OPTIONS, which is used for discovery. A
.I <password>
has to be provided, if there is a 
.I <username>
given.
.TP 
.B Lun <lun> Path=<device>,Type=(fileio|blockio)[,ScsiId=<scsi_id>][,ScsiSN=<scsi_sn>][,IOMode=(wb|ro)] | Sectors=<size>,Type=nullio
Parameters after <lun> should not contain any blank space character except the first blank space after <lun> is needed.
.br
 
.br
This line must occur at least once. The value of
.I <lun>
can be between 0 and 2^14\-1.
.br
 
.br
In
.I fileio
mode (default), it defines a mapping between a "Logical Unit Number" 
.I <lun>
and a given device
.I <device>
, which can be any block device (including regular block devices like hdX and sdX and virtual block devices like LVM and Software RAID devices) or regular files.
.br
 
.br
In
.I blockio
mode, it defines a mapping between a "Logical Unit Number"
.I <lun>
and a given block device
.I <device>.
This mode will perform direct block i/o with the device, bypassing page-cache for all operations.
This allows for efficient handling of non-aligned sector transfers (virtualized environments) and large block transfers (media servers).
This mode works ideally with high-end storage HBAs and for applications that either do not need caching between application and disk or need the large block throughput.
.br
 
.br
Optionally a
.I <scsi_id>
can be specified to assign a unique ID to the iSCSI volume. This is useful e.g. in conjunction with a multipath\-aware initiator host accessing the same
.I <device>
through several targets.
The
.I <scsi_id>
must not exceed 16 characters and controls the content of VPD 0x83. The
.I <scsi_sn>
must not exceed 16 characters and controls the content VPD 0x80.
.br
 
.br
By default, LUNs are writable, employing write-through caching. By setting
.I IOMode
to "ro" a LUN can only be accessed read only. Setting
.I IOMode
to "wb" will enable write-back caching.
Please note that this could lead to data loss e.g. in case of power outages, so it is strongly recommended to use an UPS when enabling write-back caching.
NOTE:
.I IOMode
"wb" is ignored when employing blockio.
.br
 
.br
In
.I nullio
mode, it defines a mapping between a "Logical Unit Number"
.I <lun>
and an unnamed virtual device with
.I <size>
sectors. This is ONLY useful for performance measurement purposes. All writes to this virtual device will be discarded and reads will return random data.
.TP 
.B [Alias <aliasname>]
This assigns an optional 
.I <aliasname>
to the target.
.TP 
.B [HeaderDigest <CRC32C|None>]
Optional. If set to "CRC32C" and the initiator is configured accordingly, the integrity of an iSCSI PDU's header segments will be protected by a CRC32C checksum. The default is "None". Note that header digests are not supported during discovery sessions.
.TP 
.B [DataDigest <CRC32C|None>]
Optional. If set to "CRC32C" and the initiator is configured accordingly, the integrity of an iSCSI PDU's data segment will be protected by a CRC32C checksum. The default is "None". Note that data digests are not supported during discovery sessions.
.TP 
.B [MaxConnections <value>]
Optional. Has to be set to "1" (in words: one), which is also the default.
.TP 
.B [InitialR2T <Yes|No>]
Optional. If set to "Yes" (default), the initiator has to wait for the target to solicit SCSI data before sending it. Setting it to "No" allows the initiator to send a burst of
.B FirstBurstLength
bytes unsolicited right after and/or (depending on the setting of
.B ImmediateData
) together with the command. Thus setting it to "No" may improve performance.
.TP 
.B [ImmediateData <Yes|No>]
Optional. This allows the initiator to append unsolicited data to a command. To achieve better performance, this should be set to "Yes". The default is "No".
.TP 
.B [MaxRecvDataSegmentLength <value>]
Optional. Sets the maximum data segment length that can be received. The 
.I <value>
should be set to multiples of PAGE_SIZE. Currently the maximum supported value is 64 * PAGE_SIZE, e.g. 262144 if PAGE_SIZE is 4kB. Configuring too large values may lead to problems allocating sufficient memory, which in turn may lead to SCSI commands timing out at the initiator host. The default value is 8192.
.TP 
.B [MaxXmitDataSegmentLength <value>]
Optional. Sets the maximum data segment length that can be sent. The
.I <value>
actually used is the minimum of
.B MaxXmitDataSegmentLength
and the
.B MaxRecvDataSegmentLength
announced by the initiator. The 
.I <value>
should be set to multiples of PAGE_SIZE. Currently the maximum supported value is 64 * PAGE_SIZE, e.g. 262144 if PAGE_SIZE is 4kB. Configuring too large values may lead to problems allocating sufficient memory, which in turn may lead to SCSI commands timing out at the initiator host. The default value is 8192.
.TP 
.B [MaxBurstLength <value>]
Optional. Sets the maximum amount of either unsolicited or solicited data the initiator may send in a single burst. Any amount of data exceeding this value must be explicitly solicited by the target. The 
.I <value>
should be set to multiples of PAGE_SIZE. Configuring too large values may lead to problems allocating sufficient memory, which in turn may lead to SCSI commands timing out at the initiator host. The default value is 262144.
.TP 
.B [FirstBurstLength <value>]
Optional. Sets the amount of unsolicited data the initiator may transmit in the first burst of a transfer either with and/or right after the command, depending on the settings of
.B InitialR2T
and
.B ImmediateData
.
.I <value>
should be set to multiples of PAGE_SIZE. Configuring too large values may lead to problems allocating sufficient memory, which in turn may lead to SCSI commands timing out at the initiator host. The default value is 65536.
.TP 
.B [DefaultTime2Wait <value>]
Currently not supported.
.TP 
.B [DefaultTime2Retain <value>]
Currently not supported.
.TP 
.B [MaxOutstandingR2T <value>]
Optional. Controls the maximum number of data transfers the target may request at once, each of up to
.B MaxBurstLength
bytes. The default is 1.
.TP 
.B [DataPDUInOrder <Yes|No>]
Optional. Has to be set to "Yes" \- which is also the default.
.TP 
.B [DataSequenceInOrder <Yes|No>]
Optional. Has to be set to "Yes" \- which is also the default.
.TP 
.B [ErrorRecoveryLevel <value>]
Optional. Has to be set to "0" (in words: zero), which is also the default.
.TP 
.B [Wthreads <value>]
Optional. The iSCSI target employs several threads to perform the actual block I/O to the device. Depending on your hardware and your (expected) workload, the number of these threads may be carefully adjusted. The default value of 8 should be sufficient for most purposes.
.TP 
.B [QueuedCommands <value>]
Optional. This parameter defines a window of commands an initiator may send and that will be buffered by the target. Depending on your hardware and your (expected) workload, the
.I value
may be carefully adjusted. The default value of 32 should be sufficient for most purposes.
.SH "KNOWN BUGS/LIMITATIONS"
Currently (as of 0.4.11) not all iSCSI target parameters are used. Header and data digests are not supported during discovery sessions.
.SH "SEE ALSO"
.B ietd (8)
.TP 
You should have a look at
.B RFC 3720
for all the glory details.