System Administration Commands 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 hotsparepool]
/sbin/metainit [generic options] mirror -m submirror
[readoptions] [writeoptions]
[passnum]
/sbin/metainit [generic options] RAID -r component...
[-i interlace]
[-h hotsparepool] [-k] [-o originalcolumncount]
/sbin/metainit [generic options] hotsparepool
[hotspare...]
/sbin/metainit [generic options] metadevice-name
/sbin/metainit [generic options] -a
/sbin/metainit [generic options] softpart -p [-e] component
[-A alignment] 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.
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Solaris Volume Manager supports storage devices and logical
volumes greater than 1 terabyte (TB) when a system runs a
64-bit Solaris 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
intervention.
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 prior to the Solaris 9 4/03
release, Solaris Volume Manager does not start. You must
remove all large volumes before Solaris Volume Manager runs
under an earlier version of the Solaris Operating System.
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).
Solaris Volume Manager never updates the /etc/lvm/md.tab
file. Complete configuration information is stored in the
metadevice state database, not md.tab. The only way informa-
tion 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.
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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, or if the stripe being created is smaller
in size than the underlying soft partition. 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 metadevice
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
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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/c0t0d0s0. 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 Solaris
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 512 kilobytes.
-h hotsparepool
Specifies the hotsparepool 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.
Use /-h hspnnn when the concat/stripe being created is
to be used as a submirror.
Names for hot spare pools can be any legal file name
that is composed of alphanumeric characters, a dash ("-
"), an underscore (""), or a period ("."). Names must
begin with a letter. The words "all" and "none" are
reserved and cannot be used.
Mirror Options
The following mirror options are supported:
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mirror -m submirror
Specifies the metadevice name of the mirror. The -m
indicates that the configuration is a mirror. submirror
is a metadevice (stripe or concatentation) that makes up
the initial one-way mirror. Solaris Volume Manager sup-
ports a maximum of four-way mirroring. When defining
mirrors, first create the mirror with the metainit com-
mand as a one-way mirror. Then attach subsequent submir-
rors using the metattach command. This method ensures
that Solaris Volume Manager properly syncs the mirrors.
(The second and any subsequent submirrors are first
created using the metainit command.)
readoptions
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 cannot 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 submir-
rors.
writeoptions
The following write options for mirrors are supported:
-S
Performs serial writes to mirrors. The first submir-
ror write completes before the second is started.
This can be useful if hardware is susceptible to
partial sector failures. If -S is not specified,
writes are replicated and dispatched to all mirrors
simultaneously.
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passnum
A number in the range 0-9 at the end of an entry defin-
ing 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 available:
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 previ-
ously 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, Solaris 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 originalcolumncount
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 neces-
sary 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, Solaris Volume
Manager might begin fabricating data. Instead of using
the -o option, you might want to initialize the device
and restore data from tape.
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Soft Partition Options
The following soft partition options are supported:
softpart -p [-e] component [-A alignment] 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 com-
ponent as c*t*d* should be repartitioned and reserved
for soft partitions. The specified component is reparti-
tioned such that slice 7 reserves space for system
(state database replica) usage and slice 0 contains 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 determines
the space to use for the soft partition and can be
specified in K or k for kilobytes, M or m for megabytes,
G or g for gigabytes, T or t for terabyte (one terabyte
is the maximum size), and B or b for blocks (sectors).
All values represent powers of 2, and upper and lower
case options are equivalent. Only integer values are
permitted.
The -A alignment option sets the value of the soft par-
tition extent alignment. This option used when it is
important specify a starting offset for the soft parti-
tion. It preserves the data alignment between the meta-
device address space and the address space of the under-
lying physical device. For example, a hardware device
that does checksumming should not have its I/O requests
divided by Solaris Volume Manager. In this case, use a
value from the hardware configuration as the value for
the alignment. When you use this option in conjunction
with a software I/O load, the alignment value
corresponds to the I/O load of the application. This
prevents I/O from being divided unnecessarily and
affecting performance.
The literal all, used instead of specifying size, speci-
fies that the soft partition should occupy all available
space on the device.
Hot Spare Pool Options
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The following hot spare pool options are supported:
hotsparepool [ hotspare... ]
When used as arguments to the metainit command,
hotsparepool defines the name for a hot spare pool,
and hotspare... is the logical name for the physical
slice(s) for availability in that pool. Names for hot
spare pools can be any legal file name that is composed
of alphanumeric characters, a dash ("-"), an underscore
(""), or a period ("."). Names must begin with a
letter. The words "all" and "none" are reserved and can-
not be used.
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, consider 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
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The following command creates a one-on-one concatenation for
the root slice. This 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 to create a
volume with an existing file system, such as root(/).
# metainit -f dl 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 these 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
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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 c0t1d0s0 c0t2d0s0 -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 c0t1d0s0 c0t2d0s0 \
c0t3d0s0 -i 16k \
3 c1t1d0s0 c1t2d0s0 c1t3d0s0 -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.
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# metainit d51 1 1 c0t1d0s0
# metainit d52 1 1 c0t2d0s0
# 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 with 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 Creating a metadevice in a diskset
This example shows a metadevice, /dev/md/dsk/d75, consisting
of a concatenation of two stripes within a diskset called
set1.
# metainit -s set1 d75 2 3 c2t1d0s0 c2t2d0s0 \
c2t3d0s0 -i 32k
# metainit -s set1 d51 1 1 c2t1d0s0
# metainit -s set1 d52 1 1 c3t1d0s0
# metainit -s set1 d50 -m d51
# metattach -s set1 d50 d52
In this example, a diskset is created using the metaset com-
mand. Metadevices are then created within the diskset using
the metainit command. The two submirrors, d51 and d52, are
simple concatenations. Next, a one-way mirror, d50, is
created using the -m option with 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
submirrors.
Example 7 RAID Level 5
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This example shows a RAID level 5 device, d80, consisting of
three slices:
# metainit d80 -r c1t0d0s0 c1t1d0s0 c1t3d0s0 -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, c1t0d0s0,
c1t2d0s0, and c1t3d0s0.
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 9G
In this example, the disk is repartitioned and a soft parti-
tion is defined to occupy all 9 Gbytes of disk c3t4d0s0.
Example 10 Soft Partition Taking All Available Space
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The following example shows a soft partition device, d1,
built on disk c3t4d0:
# metainit d1 -p -e c3t4d0 all
In this example, the disk is repartitioned and a soft parti-
tion is defined to occupy all available disk space on slice
c3t4d0s0.
Example 11 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 c2t2d0s0 c3t2d0s0 c1t2d0s0
# metainit d41 1 1 c1t0d0s0 -h hsp001
# metainit d42 1 1 c3t0d0s0 -h hsp001
# metainit d40 -m d41
# metattach d40 d42
In this example, a hot spare pool, hsp001, is created with
three slices from three different 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 sub-
mirror. A one-way mirror is then defined using the -m
option. The second submirror is attached using the metattach
command.
Example 12 Setting the Value of the Soft Partition Extent
Alignment
This example shows how to set the alignment of the soft par-
tition to 1 megabyte.
# metainit -s red d13 -p c1t3d0s4 -A 1m 4m
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In this example the soft partition, d13, is created with an
extent alignment of 1 megabyte. The metainit command uses
the -A option with an alignment of 1m to define the soft
partition extent alignment.
FILES
/etc/lvm/md.tab
Contains list of metadevice and hot spare configurations
for batch-like creation.
WARNINGS
This section contains information on different types of
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
prior to Solaris 10.
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 ERORS in metainit(1M) for additional information.
Truncation of Soft Partitions
When creating stripes on top of soft partitions it is possi-
ble for the size of the new stripe to be less than the size
of the underlying soft partition. If this occurs, metainit
fails with an error indicating the actions required to over-
come the failure.
If you use the -f option to override this behavior, the fol-
lowing message is displayed:
WARNING: This form of metainit is not recommended.
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The stripe is truncating the size of the underlying device.
Please see ERORS 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. Solaris Volume Manager uses
this dirty-bit technique when it can. Unfortunately, this
technique does not work for raw I/O or direct I/O. By
default, Solaris 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 associ-
ated 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 can 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 mdmirror:mdmirrorwowflg=0x20
Setting this flag degrades performance.
EXIT STATUS
The following exit values are returned:
0
Successful completion.
>0
An error occurred.
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ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWmdr
Interface Stability Stable
SEE ALSO
mdmonitord(1M), metaclear(1M), metadb(1M), metadetach(1M),
metahs(1M), metaoffline(1M), metaonline(1M), metaparam(1M),
metarecover(1M), metarename(1M), metareplace(1M),
metaroot(1M), metaset(1M), metassist(1M), metastat(1M),
metasync(1M), metattach(1M), md.tab(4), md.cf(4),
mddb.cf(4), md.tab(4), attributes(5), md(7D)
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.
NOTES
Trans metadevices have been replaced by UFS logging. Exist-
ing trans devices are not logging--they pass data directly
through to the underlying device. See mountufs(1M) for more
information about UFS logging.
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