metainit(1M)
NAME
metainit - configure metadevices
SYNOPSIS
/sbin/metainit -h
/sbin/metainit [generic options] concat/stripe numstripes
width component... [-i interlace]
/sbin/metainit [ width component... [-i interlace]] [-
h hot_spare_pool]
/sbin/metainit [generic options] mirror -m submirror
[read_options] [write_options] [pass_num]
/sbin/metainit [generic options] RAID -r component... [-
i interlace] [-h hot_spare_pool] [-k] [-
o original_column_count]
/sbin/metainit [generic options] trans -t master [log]
/sbin/metainit [generic options] hot_spare_pool
[hotspare...]
/sbin/metainit [generic options] metadevice-name
/sbin/metainit [generic options] -a
/sbin/metainit [generic options] softpart -p [-e] component
size
/sbin/metainit -r
DESCRIPTION
The metainit command configures metadevices and hot spares
according to the information specified on the command line.
Alternatively, you can run metainit so that it uses confi-
guration entries you specify in the /etc/lvm/md.tab file
(see md.tab(4)). All metadevices must be set up by the
metainit command before they can be used.
Solaris Volume Manager supports storage devices and logical
volumes greater than 1 terabyte (TB) when Solaris is running
a 64-bit kernel. Support for large volumes is automatic. If
a device greater than 1 TB is created, Solaris Volume
Manager configures it appropriately and without user inter-
vention.
If a system with large volumes is rebooted under a 32-bit
Solaris kernel, the large volumes are visible through metas-
tat output. Large volumes cannot be accessed, modified or
deleted, and no new large volumes can be created. Any
volumes or file systems on a large volume in this situation
are unavailable. If a system with large volumes is rebooted
under a version of Solaris that lacks large volume support,
Solaris Volume Manager will not start. You must remove all
large volumes before Solaris Volume Manager runs under
another version of the Solaris Operating Environment.
If you edit the /etc/lvm/md.tab file to configure metadev-
ices, specify one complete configuration entry per line. You
then run the metainit command with either the -a option, to
activate all metadevices you entered in the /etc/lvm/md.tab
file, or with the metadevice name corresponding to a
specific configuration entry.
metainit does not maintain the state of the volumes that
would have been created when metainit is run with both the
-a and -n flags. Any volumes in md.tab that have dependen-
cies on other volumes in md.tab are reported as errors when
metainit -a -n is run, although the operations might succeed
when metainit -a is run. See md.tab(4).
Volume Manager never updates the /etc/lvm/md.tab file. Com-
plete configuration information is stored in the metadevice
state database, not md.tab. The only way information appears
in md.tab is through editing it by hand.
When setting up a disk mirror, the first step is to use
metainit create a one-on-one concatenation for the root
slice. See EXAMPLES.
OPTIONS
The following options are supported:
Generic Options
Root privileges are required for all of the following
options except -h.
The following generic options are supported:
-f Forces the metainit command to continue even if one of
the slices contains a mounted file system or is being
used as swap. This option is required when configuring
mirrors on root (/), swap, and /usr.
-h Displays usage message.
-n Checks the syntax of your command line or md.tab entry
without actually setting up the metadevice. If used
with -a, all devices are checked but not initialized.
-r Only used in a shell script at boot time. Sets up all
metadevices that were configured before the system
crashed or was shut down. The information about previ-
ously configured metadevices is stored in the metadev-
ice state database (see metadb(1M)).
-s setname
Specifies the name of the diskset on which metainit
works. Without the -s option, the metainit command
operates on your local metadevices and/or hotspares.
CONCAT/STRIPE OPTIONS
The following concat/stripe options are supported:
concat/stripe
Specifies the metadevice name of the concatenation,
stripe, or concatenation of stripes being defined.
numstripes
Specifies the number of individual stripes in the
metadevice. For a simple stripe, numstripes is always
1. For a concatenation, numstripes is equal to the
number of slices. For a concatenation of stripes,
numstripes varies according to the number of stripes.
width Specifies the number of slices that make up a stripe.
When width is greater than 1, the slices are striped.
component
The logical name for the physical slice (partition) on
a disk drive, such as /dev/dsk/c0t0d0s2. For RAID
level 5 metadevices, a minimum of three slices is
necessary to enable striping of the parity information
across slices.
-i interlace
Specifies the interlace size. This value tells Volume
Manager how much data to place on a slice of a striped
or RAID level 5 metadevice before moving on to the
next slice. interlace is a specified value, followed
by either `k' for kilobytes, `m' for megabytes, or `b'
for blocks. The characters can be either uppercase or
lowercase. The interlace specified cannot be less than
16 blocks, or greater than 100 megabytes. If interlace
is not specified, it defaults to 16 kilobytes.
-h hot_spare_pool
Specifies the hot_spare_pool to be associated with the
metadevice. If you use the command line, the hot spare
pool must have been previously created by the metainit
command before it can be associated with a metadevice.
The hot_spare_pool must be of the form hspnnn, where
nnn is a number in the range 000-999. Use /-h hspnnn
when the concat/stripe being created is to be used as
a submirror.
MIRROR OPTIONS
The following mirror options are supported:
mirror -m submirror
Specifies the metadevice name of the mirror. The -m
indicates that the configuration is a mirror. submir-
ror is a metadevice (stripe or concatentation) that
makes up the initial one-way mirror. Volume Manager
supports a maximum of four-way mirroring. When defin-
ing mirrors, first create the mirror with the metainit
command as a one-way mirror. Then attach subsequent
submirrors using the metattach command. This method
ensures that Volume Manager properly syncs the mir-
rors. (The second and any subsequent submirrors are
first created using the metainit command.)
read_options
The following read options for mirrors are supported:
-g Enables the geometric read option, which results
in faster performance on sequential reads.
-r Directs all reads to the first submirror. This
should only be used when the devices comprising
the first submirror are substantially faster
than those of the second mirror. This flag can-
not be used with the -g flag.
If neither the -g nor -r flags are specified, reads
are made in a round-robin order from all submirrors in
the mirror. This enables load balancing across the
submirrors.
write_options
The following write options for mirrors are supported:
-S Performs serial writes to mirrors. The first
submirror write completes before the second is
started. This may be useful if hardware is sus-
ceptible to partial sector failures. If -S is
not specified, writes are replicated and
dispatched to all mirrors simultaneously.
pass_num
A number in the range 0-9 at the end of an entry
defining a mirror that determines the order in which
that mirror is resynced during a reboot. The default
is 1. Smaller pass numbers are resynced first. Equal
pass numbers are run concurrently. If 0 is used, the
resync is skipped. 0 should be used only for mirrors
mounted as read-only, or as swap.
RAID Level 5 OPTIONS
The following RAID level 5 options are supported:
RAID -r
Specifies the name of the RAID level 5 metadevice. The
-r specifies that the configuration is RAID level 5.
-k For RAID level 5 metadevices, informs the driver that
it is not to initialize (zero the disk blocks) due to
existing data. Only use this option to recreate a pre-
viously created RAID level 5 device.
Use the -k option with extreme caution. This option
sets the disk blocks to the OK state. If any errors
exist on disk blocks within the metadevice, Volume
Manager might begin fabricating data. Instead of using
the -k option, you might want to initialize the device
and restore data from tape.
-o original_column_count
For RAID level 5 metadevices, used with the -k option
to define the number of original slices in the event
the originally defined metadevice was grown. This is
necessary since the parity segments are not striped
across concatenated devices.
Use the -o option with extreme caution. This option
sets the disk blocks to the OK state. If any errors
exist on disk blocks within the metadevice, Volume
Manager might begin fabricating data. Instead of using
the -o option, you might want to initialize the device
and restore data from tape.
TRANS OPTIONS
The following trans options are supported:
trans -t master [ log ]
trans specifies the name of the trans metadevice,
which consists of master and log devices, or just a
master device. The -t specifies that the configuration
is a trans metadevice. If log is not specified when
you create the trans metadevice, no logging can take
place until a logging device is provided by using the
metattach command. master and log can be simple, mir-
ror, or RAID level 5 metadevices. They cannot be trans
metadevices. master should be a UFS file system. You
can configure an existing file system for logging by
creating a trans metadevice as follows: make the
existing file system into the master trans device,
then create the log device on a separate, unused
slice. The minimum log size is 1 Mbyte of disk space.
Under heavy sustained loads, small logs detract from
performance because old data must be copied from the
log to the file system before new data can be logged.
The maximum log size is 1 Gbyte. Large logs might
increase performance. However, logs larger than 64
Mbytes can have negligible performance benefits.
SOFT PARTITION OPTIONS
The following soft partition options are supported:
softpart -p [-e] component size
The softpart argument specifies the name of the soft
partition. The -p specifies that the configuration is
a soft partition.
The -e specifies that the entire disk specified by
component as c*t*d* should be repartitioned and
reserved for soft partitions. The specified component
is repartitioned such that slice 7 reserves space for
system (state database replica) usage and slice 0 con-
tains all remaining space on the disk. Slice 7 is a
minimum of 4MB, but can be larger, depending on the
disk geometry. The newly created soft partition is
placed on slice 0 of the device.
The component argument specifies the disk (c*t*d*),
slice (c*t*d*s*), or meta device (d*) from which to
create the soft partition. The size argument deter-
mines the space to use for the soft partition alnd can
be specified in K or k for kilobytes, M or m for mega-
bytes, G or g for gigabytes, T or t for terabyte (one
terabyte is the maximum size), and B or b for blocks
(sectors).
HOT SPARE POOL OPTIONS
The following hot spare pool options are supported:
hot_spare_pool [ hotspare... ]
When used as arguments to the metainit command,
hot_spare_pool defines the name for a hot spare pool,
and hotspare... is the logical name for the physical
slice(s) for availability in that pool. hot_spare_pool
is a number of the form hspnnn, where nnn is a number
in the range 000-999.
md.tab FILE OPTIONS
The following md.tab file options are supported:
metadevice-name
When the metainit command is run with a metadevice-
name as its only argument, it searches the
/etc/lvm/md.tab file to find that name and its
corresponding entry. The order in which entries appear
in the md.tab file is unimportant. For example, con-
sider the following md.tab entry:
d0 2 1 c1t0d0s0 1 c2t1d0s0
When you run the command metainit d0, it configures
metadevice d0 based on the configuration information
found in the md.tab file.
-a Activates all metadevices defined in the md.tab file.
metainit does not maintain the state of the volumes
that would have been created when metainit is run with
both the -a and -n flags. If a device d0 is created in
the first line of the md.tab file, and a later line in
md.tab assumes the existence of d0, the later line
fails when metainit -an runs (even if it would succeed
with metainit -a).
EXAMPLES
Example 1: Creating a One-on-One Concatenation
The following command creates a one-on-one concatenation for
the root slice. Such a command is the first step you take
when setting up a mirror for the root slice (and any other
slice that cannot be unmounted). The -f option is required
it create a volume with an existing file system.
# metainit -f d1 1 1 c0t0d0s0
The preceding command makes d1 a one-on-one concatenation,
using the root slice. You can then enter:
# metainit d0 -m d1
...to make a one-way mirror of the root slice.
Example 2: Concatenation
All drives in the following examples have the same size of
525 Mbytes.
This example shows a metadevice, /dev/md/dsk/d7, consisting
of a concatenation of four slices.
# metainit d7 4 1 c0t1d0s0 1 c0t2d0s0 1 c0t3d0s0 1 /dev/dsk/c0t4d0s0
The number 4 indicates there are four individual stripes in
the concatenation. Each stripe is made of one slice, hence
the number 1 appears in front of each slice. The first disk
sector in all of the above devices contains a disk label. To
preserve the labels on devices /dev/dsk/c0t2d0s0,
/dev/dsk/c0t3d0s0, and /dev/dsk/c0t4d0s0, the metadisk
driver must skip at least the first sector of those disks
when mapping accesses across the concatenation boundaries.
Because skipping only the first sector would create an
irregular disk geometry, the entire first cylinder of these
disks is skipped. This allows higher level file system
software to optimize block allocations correctly.
Example 3: Stripe
This example shows a metadevice, /dev/md/dsk/d15, consisting
of two slices.
# metainit d15 1 2 c0t1d0s2 c0t2d0s2 -i 32k
The number 1 indicates that one stripe is being created.
Because the stripe is made of two slices, the number 2 fol-
lows next. The optional -i followed by 32k specifies the
interlace size as 32 Kbytes. If the interlace size were not
specified, the stripe would use the default value of 16
Kbytes.
Example 4: Concatentation of Stripes
This example shows a metadevice, /dev/md/dsk/d75, consisting
of a concatenation of two stripes of three disks.
# metainit d75 2 3 c0t1d0s2 c0t2d0s2 \
c0t3d0s2 -i 16k \
3 c1t1d0s2 c1t2d0s2 c1t3d0s2 -i 32k
On the first line, the -i followed by 16k specifies that the
stripe interlace size is 16 Kbytes. The second set specifies
the stripe interlace size as 32 Kbytes. If the second set
did not specify 32 Kbytes, the set would use the default
interlace value of 16 Kbytes. The blocks of each set of
three disks are interlaced across three disks.
Example 5: Mirroring
This example shows a two-way mirror, /dev/md/dsk/d50, con-
sisting of two submirrors. This mirror does not contain any
existing data.
# metainit d51 1 1 c0t1d0s2
# metainit d52 1 1 c0t2d0s2
# metainit d50 -m d51
# metattach d50 d52
In this example, two submirrors, d51 and d52, are created
with the metainit command. These two submirrors are simple
concatenations. Next, a one-way mirror, d50, is created
using the -m option wtih d51. The second submirror is
attached later using the metattach command. When creating a
mirror, any combination of stripes and concatenations can be
used. The default read and write options in this example are
a round-robin read algorithm and parallel writes to all sub-
mirrors.
Example 6: Logging (trans)
This example shows trans metadevice, /dev/md/dsk/d1, with
mirrors for the master and logging devices. This trans does
not contain any existing data.
# metainit d11 1 1 c0t1d0s2
# metainit d12 1 1 c0t2d0s2
# metainit d21 1 1 c1t1d0s3
# metainit d22 1 1 c1t2d0s3
# metainit d10 -m d11
# metattach d10 d12
# metainit d20 -m d21
# metattach d20 d22
# metainit d1 -t d10 d20
This example begins by defining four concatenations, d11,
d12, d21, and d22. Next, mirror d10 is defined, followed by
mirror d20. The mirrors are initially defined as one-way
mirrors, then the second submirrors are attached later with
the metattach command. Finally, the trans metadevice d1 is
defined, with d10 as the master device and d20 as the log-
ging device by using the -t option.
Example 7: RAID Level 5
This example shows a RAID level 5 device, d80, consisting of
three slices:
# metainit d80 -r c1t0d0s2 c1t1d0s2 c1t3d0s2 -i 20k
In this example, a RAID level 5 metadevice is defined using
the -r option with an interlace size of 20 Kbytes. The data
and parity segments are striped across the slices, c1t0d0s2,
c1t2d0s2, and c1t3d0s2.
Example 8: Soft Partition
The following example shows a soft partition device, d1,
built on metadevice d100 and 100 Mbytes (indicated by 100M)
in size:
# metainit d1 -p d100 100M
The preceding command creates a 100-Mbyte soft partition on
the d100 metadevice. This metadevice could be a RAID level
5, stripe, concatenation, or mirror.
Example 9: Soft Partition on Full Disk
The following example shows a soft partition device, d1,
built on disk c3t4d0:
# metainit d1 -p -e c3t4d0 9Gb
In this example, the disk is repartitioned and a soft parti-
tion is defined to occupy all 9 Gbytes of disk c3t4d0s0.
Example 10: Hot Spare
This example shows a two-way mirror, /dev/md/dsk/d10, and a
hot spare pool with three hot spare components. The mirror
does not contain any existing data.
# metainit hsp001 c2t2d0s2 c3t2d0s2 c1t2d0s2
# metainit d41 1 1 c1t0d0s2 -h hsp001
# metainit d42 1 1 c3t0d0s2 -h hsp001
# metainit d40 -m d41
# metattach d40 d42
In the above example, a hot spare pool, hsp001, is created
with three disks used as hot spares. Next, two submirrors
are created, d41 and d42. These are simple concatenations.
The metainit command uses the -h option to associate the hot
spare pool hsp001 with each submirror. A one-way mirror is
then defined using the -m option. The second submirror is
attached using the metattach command.
FILES
/etc/lvm/md.tab
Contains list of metadevice and hot spare configura-
tions for batch-like creation.
WARNINGS
This section contains information on warnings.
Devices and Volumes Greater Than 1 TB
Do not create large (>1 TB) volumes if you expect to run the
Solaris Operating Environment with a 32-bit kernel or if you
expect to use a version of the Solaris Operating Environment
that lacks large volume support.
Multi-Way Mirror
Do not use the metainit command to create a multi-way mir-
ror. Rather, create a one-way mirror with metainit then
attach additional submirrors with metattach. When the metat-
tach command is not used, no resync operations occur and
data could become corrupted.
If you use metainit to create a mirror with multiple submir-
rors, the following message is displayed:
WARNING: This form of metainit is not recommended.
The submirrors may not have the same data.
Please see ERRORS in metainit(1M) for additional information.
Write-On-Write Problem
When mirroring data in Solaris Volume Manager, transfers
from memory to the disks do not all occur at exactly the
same time for all sides of the mirror. If the contents of
buffers are changed while the data is in-flight to the disk
(called write-on-write), then different data can end up
being stored on each side of a mirror.
This problem can be addressed by making a private copy of
the data for mirror writes, however, doing this copy is
expensive. Another approach is to detect when memory has
been modified across a write by looking at the dirty-bit
associated with the memory page. Volume Manager uses this
dirty-bit technique when it can. Unfortunately, this tech-
nique does not work for raw I/O or direct I/O. By default,
Volume Manager is tuned for performance with the liability
that mirrored data might be out of sync if an application
does a "write-on-write" to buffers associated with raw I/O
or direct I/O.
Without mirroring, you were not guaranteed what data would
actually end up on media, but multiple reads would return
the same data. With mirroring, multiple reads may return
different data. The following line can be added to
/etc/system to cause a stable copy of the buffers to be used
for all raw I/O and direct I/O write operations.
set md_mirror:md_mirror_wow_flg=0x20
Setting this flag degrades performance.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
>0 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWmdr |
|_____________________________|_____________________________|
SEE ALSO
metaclear(1M), metadb(1M), metadetach(1M), metahs(1M),
metaoffline(1M), metaonline(1M), metaparam(1M),
metarecover(1M), metareplace(1M), metaroot(1M), metaset(1M),
metastat(1M), metasync(1M), metattach(1M), md.cf(4),
md.tab(4), mddb.cf(4), attributes(5)
Solaris Volume Manager Administration Guide
LIMITATIONS
Recursive mirroring is not allowed; that is, a mirror cannot
appear in the definition of another mirror.
Recursive logging is not allowed; that is, a trans metadev-
ice cannot appear in the definition of another metadevice.
Stripes, concatenations, and RAID level 5 metadevices must
consist of slices only.
Mirroring of RAID level 5 metadevices is not allowed.
Soft partitions can be built on raw devices, or on stripes,
RAID level 5, or mirrors.
RAID level 5 or stripe metadevices can be built directly on
soft partitions.
Man(1) output converted with
man2html