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The configuration file describes individual <filename>vinum</filename> objects. The definition of a simple volume might be:
drive a device /dev/da3h
volume myvol
plex org concat
sd length 512m drive a
This file describes four <filename>vinum</filename> objects:
The <emphasis>drive</emphasis> line describes a disk partition (<emphasis>drive</emphasis>) and its location relative to the underlying hardware. It is given the symbolic name <emphasis>a</emphasis>. This separation of symbolic names from device names allows disks to be moved from one location to another without confusion.
The <emphasis>volume</emphasis> line describes a volume. The only required attribute is the name, in this case <emphasis>myvol</emphasis>.
The <emphasis>plex</emphasis> line defines a plex. The only required parameter is the organization, in this case <emphasis>concat</emphasis>. No name is necessary as the system automatically generates a name from the volume name by adding the suffix <emphasis>.p</emphasis><emphasis>x</emphasis>, where <emphasis>x</emphasis> is the number of the plex in the volume. Thus this plex will be called <emphasis>myvol.p0</emphasis>.
The <emphasis>sd</emphasis> line describes a subdisk. The minimum specifications are the name of a drive on which to store it, and the length of the subdisk. No name is necessary as the system automatically assigns names derived from the plex name by adding the suffix <emphasis>.s</emphasis><emphasis>x</emphasis>, where <emphasis>x</emphasis> is the number of the subdisk in the plex. Thus <filename>vinum</filename> gives this subdisk the name <emphasis>myvol.p0.s0</emphasis>.
After processing this file, <citerefentry><refentrytitle>gvinum</refentrytitle><manvolnum>8</manvolnum></citerefentry> produces the following output:

<prompt>#</prompt> gvinum -&gt; <userinput>create config1</userinput>
Configuration summary
Drives: 1 (4 configured)
Volumes: 1 (4 configured)
Plexes: 1 (8 configured)
Subdisks: 1 (16 configured)

D a State: up Device /dev/da3h Avail: 2061/2573 MB (80%)

V myvol State: up Plexes: 1 Size: 512 MB

P myvol.p0 C State: up Subdisks: 1 Size: 512 MB

S myvol.p0.s0 State: up PO: 0 B Size: 512 MB
This output shows the brief listing format of <citerefentry><refentrytitle>gvinum</refentrytitle><manvolnum>8</manvolnum></citerefentry>. It is represented graphically in <xref linkend="vinum-simple-vol"/>.
A Simple <filename>vinum</filename> Volume
_ external ref='vinum-simple-vol' md5='__failed__'
This figure, and the ones which follow, represent a volume, which contains the plexes, which in turn contains the subdisks. In this example, the volume contains one plex, and the plex contains one subdisk.
This particular volume has no specific advantage over a conventional disk partition. It contains a single plex, so it is not redundant. The plex contains a single subdisk, so there is no difference in storage allocation from a conventional disk partition. The following sections illustrate various more interesting configuration methods.
Increased Resilience: Mirroring
The resilience of a volume can be increased by mirroring. When laying out a mirrored volume, it is important to ensure that the subdisks of each plex are on different drives, so that a drive failure will not take down both plexes. The following configuration mirrors a volume:
drive b device /dev/da4h
volume mirror
plex org concat
sd length 512m drive a
plex org concat
sd length 512m drive b
In this example, it was not necessary to specify a definition of drive <emphasis>a</emphasis> again, since <filename>vinum</filename> keeps track of all objects in its configuration database. After processing this definition, the configuration looks like:

Drives: 2 (4 configured)
Volumes: 2 (4 configured)
Plexes: 3 (8 configured)
Subdisks: 3 (16 configured)

D a State: up Device /dev/da3h Avail: 1549/2573 MB (60%)
D b State: up Device /dev/da4h Avail: 2061/2573 MB (80%)

V myvol State: up Plexes: 1 Size: 512 MB
V mirror State: up Plexes: 2 Size: 512 MB

P myvol.p0 C State: up Subdisks: 1 Size: 512 MB
P mirror.p0 C State: up Subdisks: 1 Size: 512 MB
P mirror.p1 C State: initializing Subdisks: 1 Size: 512 MB

S myvol.p0.s0 State: up PO: 0 B Size: 512 MB
S mirror.p0.s0 State: up PO: 0 B Size: 512 MB
S mirror.p1.s0 State: empty PO: 0 B Size: 512 MB
<xref linkend="vinum-mirrored-vol"/> shows the structure graphically.
A Mirrored <filename>vinum</filename> Volume
_ external ref='vinum-mirrored-vol' md5='__failed__'
In this example, each plex contains the full 512 MB of address space. As in the previous example, each plex contains only a single subdisk.
Optimizing Performance
The mirrored volume in the previous example is more resistant to failure than an unmirrored volume, but its performance is less as each write to the volume requires a write to both drives, using up a greater proportion of the total disk bandwidth. Performance considerations demand a different approach: instead of mirroring, the data is striped across as many disk drives as possible. The following configuration shows a volume with a plex striped across four disk drives:
drive c device /dev/da5h
drive d device /dev/da6h
volume stripe
plex org striped 512k
sd length 128m drive a
sd length 128m drive b
sd length 128m drive c
sd length 128m drive d
As before, it is not necessary to define the drives which are already known to <filename>vinum</filename>. After processing this definition, the configuration looks like:

Drives: 4 (4 configured)
Volumes: 3 (4 configured)
Plexes: 4 (8 configured)
Subdisks: 7 (16 configured)

D a State: up Device /dev/da3h Avail: 1421/2573 MB (55%)
D b State: up Device /dev/da4h Avail: 1933/2573 MB (75%)
D c State: up Device /dev/da5h Avail: 2445/2573 MB (95%)
D d State: up Device /dev/da6h Avail: 2445/2573 MB (95%)

V myvol State: up Plexes: 1 Size: 512 MB
V mirror State: up Plexes: 2 Size: 512 MB
V striped State: up Plexes: 1 Size: 512 MB

P myvol.p0 C State: up Subdisks: 1 Size: 512 MB
P mirror.p0 C State: up Subdisks: 1 Size: 512 MB
P mirror.p1 C State: initializing Subdisks: 1 Size: 512 MB
P striped.p1 State: up Subdisks: 1 Size: 512 MB

S myvol.p0.s0 State: up PO: 0 B Size: 512 MB
S mirror.p0.s0 State: up PO: 0 B Size: 512 MB
S mirror.p1.s0 State: empty PO: 0 B Size: 512 MB
S striped.p0.s0 State: up PO: 0 B Size: 128 MB
S striped.p0.s1 State: up PO: 512 kB Size: 128 MB
S striped.p0.s2 State: up PO: 1024 kB Size: 128 MB
S striped.p0.s3 State: up PO: 1536 kB Size: 128 MB
A Striped <filename>vinum</filename> Volume
_ external ref='vinum-striped-vol' md5='__failed__'
This volume is represented in <xref linkend="vinum-striped-vol"/>. The darkness of the stripes indicates the position within the plex address space, where the lightest stripes come first and the darkest last.

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Source string comment
(itstool) path: sect2/para
Flags
read-only
Source string location
article.translate.xml:559
String age
a year ago
Source string age
a year ago
Translation file
articles/vinum.pot, string 91