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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

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