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(itstool) path: sect2/programlisting
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Context English State
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.
Resilience and Performance
<anchor xml:id="vinum-resilience"/>With sufficient hardware, it is possible to build volumes which show both increased resilience and increased performance compared to standard <trademark class="registered">UNIX</trademark> partitions. A typical configuration file might be:
volume raid10
plex org striped 512k
sd length 102480k drive a
sd length 102480k drive b
sd length 102480k drive c
sd length 102480k drive d
sd length 102480k drive e
plex org striped 512k
sd length 102480k drive c
sd length 102480k drive d
sd length 102480k drive e
sd length 102480k drive a
sd length 102480k drive b
The subdisks of the second plex are offset by two drives from those of the first plex. This helps to ensure that writes do not go to the same subdisks even if a transfer goes over two drives.
<xref linkend="vinum-raid10-vol"/> represents the structure of this volume.
A Mirrored, Striped <filename>vinum</filename> Volume
_ external ref='vinum-raid10-vol' md5='__failed__'
Object Naming
<filename>vinum</filename> assigns default names to plexes and subdisks, although they may be overridden. Overriding the default names is not recommended as it 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 be up to 32 characters long.

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Source information

Source string comment
(itstool) path: sect2/programlisting
Flags
no-wrap, read-only
Source string location
article.translate.xml:631
String age
a year ago
Source string age
a year ago
Translation file
articles/vinum.pot, string 101