DragonFly On-Line Manual Pages

VINUM(4) DragonFly Kernel Interfaces Manual VINUM(4)

NAME
vinum - Logical Volume Manager

SYNOPSIS
pseudo-device vinum

DESCRIPTION
vinum is a logical volume manager inspired by, but not derived from, the
Veritas Volume Manager. It provides the following features:

* It provides device-independent logical disks, called volumes.
Volumes are not restricted to the size of any disk on the system.

* The volumes consist of one or more plexes, each of which contain the
entire address space of a volume. This represents an implementation
of RAID-1 (mirroring). Multiple plexes can also be used for

* Increased read throughput. vinum will read data from the least
active disk, so if a volume has plexes on multiple disks, more
data can be read in parallel. vinum reads data from only one
plex, but it writes data to all plexes.

* Increased reliability. By storing plexes on different disks,
data will remain available even if one of the plexes becomes
unavailable. In comparison with a RAID-5 plex (see below), using
multiple plexes requires more storage space, but gives better
performance, particularly in the case of a drive failure.

* Additional plexes can be used for on-line data reorganization.
By attaching an additional plex and subsequently detaching one of
the older plexes, data can be moved on-line without compromising
access.

* An additional plex can be used to obtain a consistent dump of a
file system. By attaching an additional plex and detaching at a
specific time, the detached plex becomes an accurate snapshot of
the file system at the time of detachment.

* Each plex consists of one or more logical disk slices, called
subdisks. Subdisks are defined as a contiguous block of physical
disk storage. A plex may consist of any reasonable number of
subdisks (in other words, the real limit is not the number, but other
factors, such as memory and performance, associated with maintaining
a large number of subdisks).

* A number of mappings between subdisks and plexes are available:

* Concatenated plexes consist of one or more subdisks, each of
which is mapped to a contiguous part of the plex address space.

* Striped plexes consist of two or more subdisks of equal size.
The file address space is mapped in stripes, integral fractions
of the subdisk size. Consecutive plex address space is mapped to
stripes in each subdisk in turn. The subdisks of a striped plex
must all be the same size.

* RAID-5 plexes require at least three equal-sized subdisks. They
resemble striped plexes, except that in each stripe, one subdisk
stores parity information. This subdisk changes in each stripe:
in the first stripe, it is the first subdisk, in the second it is
the second subdisk, etc. In the event of a single disk failure,
vinum will recover the data based on the information stored on
the remaining subdisks. This mapping is particularly suited to
read-intensive access. The subdisks of a RAID-5 plex must all be
the same size.

* Drives are the lowest level of the storage hierarchy. They represent
disk special devices.

* vinum offers automatic startup. Unlike UNIX file systems, vinum
volumes contain all the configuration information needed to ensure
that they are started correctly when the subsystem is enabled. This
is also a significant advantage over the Veritastm File System. This
feature regards the presence of the volumes. It does not mean that
the volumes will be mounted automatically, since the standard startup
procedures with /etc/fstab perform this function.

KERNEL CONFIGURATION
vinum is currently supplied as a KLD module, and does not require
configuration. As with other klds, it is absolutely necessary to match
the kld to the version of the operating system. Failure to do so will
cause vinum to issue an error message and terminate.

It is possible to configure vinum in the kernel, but this is not
recommended. To do so, add this line to the kernel configuration file:

pseudo-device vinum

Debug Options
The current version of vinum, both the kernel module and the user program
vinum(8), include significant debugging support. It is not recommended
to remove this support at the moment, but if you do you must remove it
from both the kernel and the user components. To do this, edit the files
/usr/src/sbin/vinum/Makefile and /sys/dev/raid/vinum/Makefile and edit
the CFLAGS variable to remove the -DVINUMDEBUG option. If you have
configured vinum into the kernel, either specify the line

options VINUMDEBUG

in the kernel configuration file or remove the -DVINUMDEBUG option from
/usr/src/sbin/vinum/Makefile as described above.

If the VINUMDEBUG variables do not match, vinum(8) will fail with a
message explaining the problem and what to do to correct it.

vinum was previously available in two versions: a freely available
version which did not contain RAID-5 functionality, and a full version
including RAID-5 functionality, which was available only from Cybernet
Systems Inc. The present version of vinum includes the RAID-5
functionality.

RUNNING VINUM
vinum is part of the base DragonFly system. It does not require
installation. To start it, start the vinum(8) program, which will load
the kld if it is not already present. Before using vinum, it must be
configured. See vinum(8) for information on how to create a vinum
configuration.

Normally, you start a configured version of vinum at boot time. Set the
variable start_vinum in /etc/rc.conf to "YES" to start vinum at boot
time. (See rc.conf(5) for more details.)

If vinum is loaded as a kld (the recommended way), the vinum stop command
will unload it (see vinum(8)). You can also do this with the
kldunload(8) command.

The kld can only be unloaded when idle, in other words when no volumes
are mounted and no other instances of the vinum(8) program are active.
Unloading the kld does not harm the data in the volumes.

Configuring and Starting Objects
Use the vinum(8) utility to configure and start vinum objects.

IOCTL CALLS
ioctl(2) calls are intended for the use of the vinum(8) configuration
program only. They are described in the header file
/sys/dev/raid/vinum/vinumio.h.

Disk Labels
Conventional disk special devices have a disk label in the second sector
of the device. See disklabel(5) for more details. This disk label
describes the layout of the partitions within the device. vinum does not
subdivide volumes, so volumes do not contain a physical disk label. For
convenience, vinum implements the ioctl calls DIOCGDINFO (get disk
label), DIOCGPART (get partition information), DIOCWDINFO (write
partition information) and DIOCSDINFO (set partition information).
DIOCGDINFO and DIOCGPART refer to an internal representation of the disk
label which is not present on the volume. As a result, the -r option of
disklabel(8), which reads the "raw disk", will fail.

In general, disklabel(8) serves no useful purpose on a vinum volume.

vinum ignores the DIOCWDINFO and DIOCSDINFO ioctls, since there is
nothing to change. As a result, any attempt to modify the disk label
will be silently ignored.

MAKING FILE SYSTEMS
Since vinum volumes do not contain partitions, the names do not need to
conform to the standard rules for naming disk partitions. For a physical
disk partition, the last letter of the device name specifies the
partition identifier (a to p). vinum volumes need not conform to this
convention, but if they do not, newfs(8) will complain that it cannot
determine the partition. To solve this problem, use the -v flag to
newfs(8). For example, if you have a volume concat, use the following
command to create a UFS(5) file system on it:

newfs -v /dev/vinum/concat

OBJECT NAMING
vinum assigns default names to plexes and subdisks, although they may be
overridden. We do not recommend overriding the default names.
Experience with the Veritastm volume manager, which allows arbitrary
naming of objects, has shown that this flexibility does not bring a
significant advantage, and it can cause confusion.

Names may contain any non-blank character, but it is recommended to
restrict them to letters, digits and the underscore characters. The
names of volumes, plexes and subdisks may be up to 64 characters long,
and the names of drives may up to 32 characters long. When choosing
volume and plex names, bear in mind that automatically generated plex and
subdisk names are longer than the name from which they are derived.

* When vinum creates or deletes objects, it creates a directory
/dev/vinum, in which it makes device entries for each volume. It
also creates the subdirectories, /dev/vinum/plex and /dev/vinum/sd,
in which it stores device entries for the plexes and subdisks. In
addition, it creates two more directories, /dev/vinum/vol and
/dev/vinum/drive, in which it stores hierarchical information for
volumes and drives.

* In addition, vinum creates three super-devices, /dev/vinum/control,
/dev/vinum/Control and /dev/vinum/controld. /dev/vinum/control is
used by vinum(8) when it has been compiled without the VINUMDEBUG
option, /dev/vinum/Control is used by vinum(8) when it has been
compiled with the VINUMDEBUG option, and /dev/vinum/controld is used
by the vinum daemon. The two control devices for vinum(8) are used
to synchronize the debug status of kernel and user modules.

* Unlike UNIX drives, vinum volumes are not subdivided into partitions,
and thus do not contain a disk label. Unfortunately, this confuses a
number of utilities, notably newfs(8), which normally tries to
interpret the last letter of a vinum volume name as a partition
identifier. If you use a volume name which does not end in the
letters `a' to `c', you must use the -v flag to newfs(8) in order to
tell it to ignore this convention.

* Plexes do not need to be assigned explicit names. By default, a plex
name is the name of the volume followed by the letters .p and the
number of the plex. For example, the plexes of volume vol3 are
called vol3.p0, vol3.p1 and so on. These names can be overridden,
but it is not recommended.

* Like plexes, subdisks are assigned names automatically, and explicit
naming is discouraged. A subdisk name is the name of the plex
followed by the letters .s and a number identifying the subdisk. For
example, the subdisks of plex vol3.p0 are called vol3.p0.s0,
vol3.p0.s1 and so on.

* By contrast, drives must be named. This makes it possible to move a
drive to a different location and still recognize it automatically.
Drive names may be up to 32 characters long.

Example
Assume the vinum objects described in the section CONFIGURATION FILE in
vinum(8). The directory /dev/vinum looks like:

# ls -lR /dev/vinum
total 5
crwxr-xr-- 1 root wheel 91, 2 Mar 30 16:08 concat
crwx------ 1 root wheel 91, 0x40000000 Mar 30 16:08 control
crwx------ 1 root wheel 91, 0x40000001 Mar 30 16:08 controld
drwxrwxrwx 2 root wheel 512 Mar 30 16:08 drive
drwxrwxrwx 2 root wheel 512 Mar 30 16:08 plex
drwxrwxrwx 2 root wheel 512 Mar 30 16:08 rvol
drwxrwxrwx 2 root wheel 512 Mar 30 16:08 sd
crwxr-xr-- 1 root wheel 91, 3 Mar 30 16:08 strcon
crwxr-xr-- 1 root wheel 91, 1 Mar 30 16:08 stripe
crwxr-xr-- 1 root wheel 91, 0 Mar 30 16:08 tinyvol
drwxrwxrwx 7 root wheel 512 Mar 30 16:08 vol
crwxr-xr-- 1 root wheel 91, 4 Mar 30 16:08 vol5

/dev/vinum/drive:
total 0
crw-r----- 1 root operator 4, 15 Oct 21 16:51 drive2
crw-r----- 1 root operator 4, 31 Oct 21 16:51 drive4

/dev/vinum/plex:
total 0
crwxr-xr-- 1 root wheel 91, 0x10000002 Mar 30 16:08 concat.p0
crwxr-xr-- 1 root wheel 91, 0x10010002 Mar 30 16:08 concat.p1
crwxr-xr-- 1 root wheel 91, 0x10000003 Mar 30 16:08 strcon.p0
crwxr-xr-- 1 root wheel 91, 0x10010003 Mar 30 16:08 strcon.p1
crwxr-xr-- 1 root wheel 91, 0x10000001 Mar 30 16:08 stripe.p0
crwxr-xr-- 1 root wheel 91, 0x10000000 Mar 30 16:08 tinyvol.p0
crwxr-xr-- 1 root wheel 91, 0x10000004 Mar 30 16:08 vol5.p0
crwxr-xr-- 1 root wheel 91, 0x10010004 Mar 30 16:08 vol5.p1

/dev/vinum/sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20000002 Mar 30 16:08 concat.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100002 Mar 30 16:08 concat.p0.s1
crwxr-xr-- 1 root wheel 91, 0x20010002 Mar 30 16:08 concat.p1.s0
crwxr-xr-- 1 root wheel 91, 0x20000003 Mar 30 16:08 strcon.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100003 Mar 30 16:08 strcon.p0.s1
crwxr-xr-- 1 root wheel 91, 0x20010003 Mar 30 16:08 strcon.p1.s0
crwxr-xr-- 1 root wheel 91, 0x20110003 Mar 30 16:08 strcon.p1.s1
crwxr-xr-- 1 root wheel 91, 0x20000001 Mar 30 16:08 stripe.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100001 Mar 30 16:08 stripe.p0.s1
crwxr-xr-- 1 root wheel 91, 0x20000000 Mar 30 16:08 tinyvol.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100000 Mar 30 16:08 tinyvol.p0.s1
crwxr-xr-- 1 root wheel 91, 0x20000004 Mar 30 16:08 vol5.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100004 Mar 30 16:08 vol5.p0.s1
crwxr-xr-- 1 root wheel 91, 0x20010004 Mar 30 16:08 vol5.p1.s0
crwxr-xr-- 1 root wheel 91, 0x20110004 Mar 30 16:08 vol5.p1.s1

/dev/vinum/vol:
total 5
crwxr-xr-- 1 root wheel 91, 2 Mar 30 16:08 concat
drwxr-xr-x 4 root wheel 512 Mar 30 16:08 concat.plex
crwxr-xr-- 1 root wheel 91, 3 Mar 30 16:08 strcon
drwxr-xr-x 4 root wheel 512 Mar 30 16:08 strcon.plex
crwxr-xr-- 1 root wheel 91, 1 Mar 30 16:08 stripe
drwxr-xr-x 3 root wheel 512 Mar 30 16:08 stripe.plex
crwxr-xr-- 1 root wheel 91, 0 Mar 30 16:08 tinyvol
drwxr-xr-x 3 root wheel 512 Mar 30 16:08 tinyvol.plex
crwxr-xr-- 1 root wheel 91, 4 Mar 30 16:08 vol5
drwxr-xr-x 4 root wheel 512 Mar 30 16:08 vol5.plex

/dev/vinum/vol/concat.plex:
total 2
crwxr-xr-- 1 root wheel 91, 0x10000002 Mar 30 16:08 concat.p0
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 concat.p0.sd
crwxr-xr-- 1 root wheel 91, 0x10010002 Mar 30 16:08 concat.p1
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 concat.p1.sd

/dev/vinum/vol/concat.plex/concat.p0.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20000002 Mar 30 16:08 concat.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100002 Mar 30 16:08 concat.p0.s1

/dev/vinum/vol/concat.plex/concat.p1.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20010002 Mar 30 16:08 concat.p1.s0

/dev/vinum/vol/strcon.plex:
total 2
crwxr-xr-- 1 root wheel 91, 0x10000003 Mar 30 16:08 strcon.p0
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 strcon.p0.sd
crwxr-xr-- 1 root wheel 91, 0x10010003 Mar 30 16:08 strcon.p1
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 strcon.p1.sd

/dev/vinum/vol/strcon.plex/strcon.p0.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20000003 Mar 30 16:08 strcon.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100003 Mar 30 16:08 strcon.p0.s1

/dev/vinum/vol/strcon.plex/strcon.p1.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20010003 Mar 30 16:08 strcon.p1.s0
crwxr-xr-- 1 root wheel 91, 0x20110003 Mar 30 16:08 strcon.p1.s1

/dev/vinum/vol/stripe.plex:
total 1
crwxr-xr-- 1 root wheel 91, 0x10000001 Mar 30 16:08 stripe.p0
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 stripe.p0.sd

/dev/vinum/vol/stripe.plex/stripe.p0.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20000001 Mar 30 16:08 stripe.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100001 Mar 30 16:08 stripe.p0.s1

/dev/vinum/vol/tinyvol.plex:
total 1
crwxr-xr-- 1 root wheel 91, 0x10000000 Mar 30 16:08 tinyvol.p0
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 tinyvol.p0.sd

/dev/vinum/vol/tinyvol.plex/tinyvol.p0.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20000000 Mar 30 16:08 tinyvol.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100000 Mar 30 16:08 tinyvol.p0.s1

/dev/vinum/vol/vol5.plex:
total 2
crwxr-xr-- 1 root wheel 91, 0x10000004 Mar 30 16:08 vol5.p0
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 vol5.p0.sd
crwxr-xr-- 1 root wheel 91, 0x10010004 Mar 30 16:08 vol5.p1
drwxr-xr-x 2 root wheel 512 Mar 30 16:08 vol5.p1.sd

/dev/vinum/vol/vol5.plex/vol5.p0.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20000004 Mar 30 16:08 vol5.p0.s0
crwxr-xr-- 1 root wheel 91, 0x20100004 Mar 30 16:08 vol5.p0.s1

/dev/vinum/vol/vol5.plex/vol5.p1.sd:
total 0
crwxr-xr-- 1 root wheel 91, 0x20010004 Mar 30 16:08 vol5.p1.s0
crwxr-xr-- 1 root wheel 91, 0x20110004 Mar 30 16:08 vol5.p1.s1

In the case of unattached plexes and subdisks, the naming is reversed.
Subdisks are named after the disk on which they are located, and plexes
are named after the subdisk. This mapping is still to be determined.

Object States
Each vinum object has a state associated with it. vinum uses this state
to determine the handling of the object.

Volume States
Volumes may have the following states:

down The volume is completely inaccessible.

up The volume is up and at least partially functional. Not
all plexes may be available.

Plex States
Plexes may have the following states:

referenced A plex entry which has been referenced as part of a
volume, but which is currently not known.

faulty A plex which has gone completely down because of I/O
errors.

down A plex which has been taken down by the administrator.

initializing A plex which is being initialized.

The remaining states represent plexes which are at least partially up.

corrupt A plex entry which is at least partially up. Not all
subdisks are available, and an inconsistency has
occurred. If no other plex is uncorrupted, the volume is
no longer consistent.

degraded A RAID-5 plex entry which is accessible, but one subdisk
is down, requiring recovery for many I/O requests.

flaky A plex which is really up, but which has a reborn subdisk
which we do not completely trust, and which we do not
want to read if we can avoid it.

up A plex entry which is completely up. All subdisks are
up.

Subdisk States
Subdisks can have the following states:

empty A subdisk entry which has been created completely. All
fields are correct, and the disk has been updated, but
the on the disk is not valid.

referenced A subdisk entry which has been referenced as part of a
plex, but which is currently not known.

initializing A subdisk entry which has been created completely and
which is currently being initialized.

The following states represent invalid data.

obsolete A subdisk entry which has been created completely. All
fields are correct, the config on disk has been updated,
and the data was valid, but since then the drive has been
taken down, and as a result updates have been missed.

stale A subdisk entry which has been created completely. All
fields are correct, the disk has been updated, and the
data was valid, but since then the drive has been crashed
and updates have been lost.

The following states represent valid, inaccessible data.

crashed A subdisk entry which has been created completely. All
fields are correct, the disk has been updated, and the
data was valid, but since then the drive has gone down.
No attempt has been made to write to the subdisk since
the crash, so the data is valid.

down A subdisk entry which was up, which contained valid data,
and which was taken down by the administrator. The data
is valid.

reviving The subdisk is currently in the process of being revived.
We can write but not read.

The following states represent accessible subdisks with valid data.

reborn A subdisk entry which has been created completely. All
fields are correct, the disk has been updated, and the
data was valid, but since then the drive has gone down
and up again. No updates were lost, but it is possible
that the subdisk has been damaged. We won't read from
this subdisk if we have a choice. If this is the only
subdisk which covers this address space in the plex, we
set its state to up under these circumstances, so this
status implies that there is another subdisk to fulfil
the request.

up A subdisk entry which has been created completely. All
fields are correct, the disk has been updated, and the
data is valid.

Drive States
Drives can have the following states:

referenced At least one subdisk refers to the drive, but it is not
currently accessible to the system. No device name is
known.

down The drive is not accessible.

up The drive is up and running.

DEBUGGING PROBLEMS WITH VINUM
Solving problems with vinum can be a difficult affair. This section
suggests some approaches.

Configuration problems
It is relatively easy (too easy) to run into problems with the vinum
configuration. If you do, the first thing you should do is stop
configuration updates:

vinum setdaemon 4

This will stop updates and any further corruption of the on-disk
configuration.

Next, look at the on-disk configuration with the vinum dumpconfig
command, for example:

# vinum dumpconfig
Drive 4: Device /dev/da3s0h
Created on crash.lemis.com at Sat May 20 16:32:44 2000
Config last updated Sat May 20 16:32:56 2000
Size: 601052160 bytes (573 MB)
volume obj state up
volume src state up
volume raid state down
volume r state down
volume foo state up
plex name obj.p0 state corrupt org concat vol obj
plex name obj.p1 state corrupt org striped 128b vol obj
plex name src.p0 state corrupt org striped 128b vol src
plex name src.p1 state up org concat vol src
plex name raid.p0 state faulty org disorg vol raid
plex name r.p0 state faulty org disorg vol r
plex name foo.p0 state up org concat vol foo
plex name foo.p1 state faulty org concat vol foo
sd name obj.p0.s0 drive drive2 plex obj.p0 state reborn len 409600b driveoffset 265b plexoffset 0b
sd name obj.p0.s1 drive drive4 plex obj.p0 state up len 409600b driveoffset 265b plexoffset 409600b
sd name obj.p1.s0 drive drive1 plex obj.p1 state up len 204800b driveoffset 265b plexoffset 0b
sd name obj.p1.s1 drive drive2 plex obj.p1 state reborn len 204800b driveoffset 409865b plexoffset 128b
sd name obj.p1.s2 drive drive3 plex obj.p1 state up len 204800b driveoffset 265b plexoffset 256b
sd name obj.p1.s3 drive drive4 plex obj.p1 state up len 204800b driveoffset 409865b plexoffset 384b

The configuration on all disks should be the same. If this is not the
case, please save the output to a file and report the problem. There is
probably little that can be done to recover the on-disk configuration,
but if you keep a copy of the files used to create the objects, you
should be able to re-create them. The create command does not change the
subdisk data, so this will not cause data corruption. You may need to
use the resetconfig command if you have this kind of trouble.

Kernel Panics
In order to analyse a panic which you suspect comes from vinum you will
need to build a debug kernel. See the online handbook at
http://www.dragonflybsd.org/docs/user/list/DebugKernelCrashDumps/ for
more details of how to do this.

Perform the following steps to analyse a vinum problem:

1. Copy the following files to the directory in which you will be
performing the analysis, typically /var/crash:

* /sys/dev/raid/vinum/.gdbinit.crash,
* /sys/dev/raid/vinum/.gdbinit.kernel,
* /sys/dev/raid/vinum/.gdbinit.serial,
* /sys/dev/raid/vinum/.gdbinit.vinum and
* /sys/dev/raid/vinum/.gdbinit.vinum.paths

2. Make sure that you build the vinum module with debugging
information. The standard Makefile builds a module with debugging
symbols by default. If the version of vinum in /boot/kernel does
not contain symbols, you will not get an error message, but the
stack trace will not show the symbols. Check the module before
starting kgdb(1):

$ file /boot/kernel/vinum.ko
/boot/kernel/vinum.ko: ELF 32-bit LSB shared object, Intel 80386,
version 1 (SYSV), dynamically linked, not stripped

If the output shows that /boot/kernel/vinum.ko is stripped, you will
have to find a version which is not. Usually this will be either in
/usr/obj/usr/src/sys/SYSTEM_NAME/usr/src/sys/dev/raid/vinum/vinum.ko
(if you have built vinum with a "make world") or
/sys/dev/raid/vinum/vinum.ko (if you have built vinum in this
directory). Modify the file .gdbinit.vinum.paths accordingly.

3. Either take a dump or use remote serial gdb(1) to analyse the
problem. To analyse a dump, say /var/crash/vmcore.5, link
/var/crash/.gdbinit.crash to /var/crash/.gdbinit and enter:

cd /var/crash
kgdb kernel.debug vmcore.5

This example assumes that you have installed the correct debug
kernel at /var/crash/kernel.debug. If not, substitute the correct
name of the debug kernel.

To perform remote serial debugging, link /var/crash/.gdbinit.serial
to /var/crash/.gdbinit and enter

cd /var/crash
kgdb kernel.debug

In this case, the .gdbinit file performs the functions necessary to
establish connection. The remote machine must already be in debug
mode: enter the kernel debugger and select gdb (see ddb(4) for more
details.) The serial .gdbinit file expects the serial connection to
run at 38400 bits per second; if you run at a different speed, edit
the file accordingly (look for the remotebaud specification).

The following example shows a remote debugging session using the
debug command of vinum(8):

GDB 4.16 (i386-unknown-dragonfly), Copyright 1996 Free Software Foundation, Inc.
Debugger (msg=0xf1093174 "vinum debug") at ../../i386/i386/db_interface.c:318
318 in_Debugger = 0;
#1 0xf108d9bc in vinumioctl (dev=0x40001900, cmd=0xc008464b, data=0xf6dedee0 "",
flag=0x3, p=0xf68b7940) at
/usr/src/sys/dev/raid/vinum/vinumioctl.c:102
102 Debugger ("vinum debug");
(kgdb) bt
#0 Debugger (msg=0xf0f661ac "vinum debug") at ../../i386/i386/db_interface.c:318
#1 0xf0f60a7c in vinumioctl (dev=0x40001900, cmd=0xc008464b, data=0xf6923ed0 "",
flag=0x3, p=0xf688e6c0) at
/usr/src/sys/dev/raid/vinum/vinumioctl.c:109
#2 0xf01833b7 in spec_ioctl (ap=0xf6923e0c) at ../../miscfs/specfs/spec_vnops.c:424
#3 0xf0182cc9 in spec_vnoperate (ap=0xf6923e0c) at ../../miscfs/specfs/spec_vnops.c:129
#4 0xf01eb3c1 in ufs_vnoperatespec (ap=0xf6923e0c) at ../../ufs/ufs/ufs_vnops.c:2312
#5 0xf017dbb1 in vn_ioctl (fp=0xf1007ec0, com=0xc008464b, data=0xf6923ed0 "",
p=0xf688e6c0) at vnode_if.h:395
#6 0xf015dce0 in ioctl (p=0xf688e6c0, uap=0xf6923f84) at ../../kern/sys_generic.c:473
#7 0xf0214c0b in syscall (frame={tf_es = 0x27, tf_ds = 0x27, tf_edi = 0xefbfcff8,
tf_esi = 0x1, tf_ebp = 0xefbfcf90, tf_isp = 0xf6923fd4, tf_ebx = 0x2,
tf_edx = 0x804b614, tf_ecx = 0x8085d10, tf_eax = 0x36, tf_trapno = 0x7,
tf_err = 0x2, tf_eip = 0x8060a34, tf_cs = 0x1f, tf_eflags = 0x286,
tf_esp = 0xefbfcf78, tf_ss = 0x27}) at ../../i386/i386/trap.c:1100
#8 0xf020a1fc in Xint0x80_syscall ()
#9 0x804832d in ?? ()
#10 0x80482ad in ?? ()
#11 0x80480e9 in ?? ()

When entering from the debugger, it is important that the source of
frame 1 (listed by the .gdbinit file at the top of the example)
contains the text "Debugger ("vinum debug");".

This is an indication that the address specifications are correct.
If you get some other output, your symbols and the kernel module are
out of sync, and the trace will be meaningless.

For an initial investigation, the most important information is the
output of the bt (backtrace) command above.

Reporting Problems with Vinum
If you find any bugs in vinum, please report them to Greg Lehey
<grog@lemis.com>. Supply the following information:

* The output of the vinum list command (see vinum(8)).

* Any messages printed in /var/log/messages. All such messages will be
identified by the text "vinum" at the beginning.

* If you have a panic, a stack trace as described above.

SEE ALSO
disklabel(5), disklabel(8), newfs(8), vinum(8)

HISTORY
vinum first appeared in FreeBSD 3.0. The RAID-5 component of vinum was
developed by Cybernet Inc. (http://www.cybernet.com/), for its NetMAX
product.

AUTHORS
Greg Lehey <grog@lemis.com>.

BUGS
vinum is a new product. Bugs can be expected. The configuration
mechanism is not yet fully functional. If you have difficulties, please
look at the section DEBUGGING PROBLEMS WITH VINUM before reporting
problems.

Kernels with the vinum pseudo-device appear to work, but are not
supported. If you have trouble with this configuration, please first
replace the kernel with a non-vinum kernel and test with the kld module.

Detection of differences between the version of the kernel and the kld is
not yet implemented.

The RAID-5 functionality is new in FreeBSD 3.3. Some problems have been
reported with vinum in combination with soft updates, but these are not
reproducible on all systems. If you are planning to use vinum in a
production environment, please test carefully.

DragonFly 5.5-DEVELOPMENT December 12, 2014 DragonFly 5.5-DEVELOPMENT