metainit(1M) System Administration Commands metainit(1M)NAMEmetainit - configure metadevices
SYNOPSIS
/sbin/metainit -h
/sbin/metainit [generic options] concat/stripe numstripes width compo‐
nent... [-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] hot_spare_pool [hotspare...]
/sbin/metainit [generic options] metadevice-name
/sbin/metainit [generic options] -a
/sbin/metainit [generic options] softpart -p [-e] component [-A align‐
ment] 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 configuration 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 a system runs a 64-bit Solaris ker‐
nel. 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 ker‐
nel, the large volumes are visible through metastat output. Large vol‐
umes 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 metadevices, 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 corre‐
sponding 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 dependencies 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 information appears in md.tab is through edit‐
ing 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, 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 metade‐
vice 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 num‐
ber of slices. For a concatenation of stripes, num‐
stripes 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, fol‐
lowed by either `k' for kilobytes, `m' for megabytes,
or `b' for blocks. The characters can be either upper‐
case 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 kilo‐
bytes.
-h hot_spare_pooSpecifies 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. submirror is a metadevice (stripe or
concatentation) that makes up the initial one-way mirror. Solaris
Volume Manager supports a maximum of four-way mirroring. When
defining 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 Solaris Volume Manager
properly syncs the mirrors. (The second and any subsequent submir‐
rors 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 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 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 can be
useful if hardware is susceptible to partial sector fail‐
ures. 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 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 previously 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 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, 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.
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 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 cre‐
ated 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 par‐
tition. 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 equiva‐
lent. Only integer values are permitted.
The -A alignment option sets the value of the soft partition extent
alignment. This option used when it is important specify a starting
offset for the soft partition. It preserves the data alignment
between the metadevice address space and the address space of the
underlying 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, specifies that
the soft partition should occupy all available space on the device.
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 logi‐
cal 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 num‐
ber 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, 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
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 mir‐
ror 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 sys‐
tem, such as root(/).
# 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 con‐
catenation 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 con‐
catenation. 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 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 follows 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 con‐
catenation 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 inter‐
lace 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, consisting of two
submirrors. This mirror does not contain any existing data.
# 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 submirrors.
Example 6: Creating a metadevice in a diskset
This example shows a metadevice, /dev/md/dsk/d75, consisting of a con‐
catenation 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 command.
Metadevices are then created within the diskset using the metainit com‐
mand. 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
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 seg‐
ments 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, concatena‐
tion, 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 partition is
defined to occupy all 9 Gbytes of disk c3t4d0s0.
Example 10: Soft Partition Taking All Available Space
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 partition 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 submirror. 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 partition to 1
megabyte.
# metainit-s red d13 -p c1t3d0s4 -A 1m 4m
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 mirror. Rather,
create a one-way mirror with metainit then attach additional submirrors
with metattach. When the metattach command is not used, no resync oper‐
ations occur and data could become corrupted.
If you use metainit to create a mirror with multiple submirrors, 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.
Truncation of Soft Partitions
When creating stripes on top of soft partitions it is possible 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 overcome the failure.
If you use the -f option to override this behavior, the following mes‐
sage is displayed:
WARNING: This form of metainit is not recommended.
The stripe is truncating the size of the underlying device.
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. Solaris 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, Solaris Vol‐
ume 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 mul‐
tiple reads would return the same data. With mirroring, multiple reads
can return different data. The following line can be added to /etc/sys‐
tem 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 attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWmdr │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOmdmonitord(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), metas‐
sist(1M), metastat(1M), metasync(1M), metattach(1M), md.tab(4),
md.cf(4), mddb.cf(4), md.tab(4), attributes(5), md(7D)
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 metadevice 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 parti‐
tions.
NOTES
Trans metadevices have been replaced by UFS logging. Existing trans
devices are not logging--they pass data directly through to the under‐
lying device. See mount_ufs(1M) for more information about UFS logging.
SunOS 5.10 20 Sep 2004 metainit(1M)
