Previous Sections

Introduction
The problems
Current implementations
How Vinum addresses the Three Problems
The big picture
Some examples
Increased resilience: RAID-5

Object naming

As described above, Vinum assigns default names to plexes and subdisks, although they may be overridden. Overriding the default names is not recommended: experience with the VERITAS volume manager, which allows arbitary naming of objects, has shown that this flexibility 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 up to 32 characters long.

Vinum objects are assigned device nodes in the hierarchy /dev/vinum. The configuration shown above would cause Vinum to create the following device nodes:

• The control devices /dev/vinum/control and /dev/vinum/controld, which are used by vinum(8) and the Vinum dæmon respectively.
• Block and character device entries for each volume. These are the main devices used by Vinum. The block device names are the name of the volume, while the character device names follow the BSD tradition of prepending the letter r to the name. Thus the configuration above would include the block devices /dev/vinum/myvol, /dev/vinum/mirror, /dev/vinum/striped, /dev/vinum/raid5 and /dev/vinum/raid10, and the character devices /dev/vinum/rmyvol, /dev/vinum/rmirror, /dev/vinum/rstriped, /dev/vinum/rraid5 and /dev/vinum/rraid10. There is obviously a problem here: it is possible to have two volumes called r and rr, but there will be a conflict creating the device node /dev/vinum/rr: is it a character device for volume r or a block device for volume rr? Currently Vinum does not address this conflict: the first-defined volume will get the name.
• A directory /dev/vinum/drive with entries for each drive. These entries are in fact symbolic links to the corresponding disk nodes.
• A directory /dev/vinum/volume with entries for each volume. It contains subdirectories for each plex, which in turn contain subdirectories for their component subdisks.
• The directories /dev/vinum/plex and /dev/vinum/sd, /dev/vinum/rsd, which contain block device nodes for each plex and block and character device nodes respectively for subdisk.

For example, consider the following configuration file:

drive drive1 device /dev/sd1h
drive drive2 device /dev/sd2h
drive drive3 device /dev/sd3h
drive drive4 device /dev/sd4h
volume s64 setupstate
 plex org striped 64k
   sd length 100m drive drive1
   sd length 100m drive drive2
   sd length 100m drive drive3
   sd length 100m drive drive4

After processing this file, vinum(8) creates the following structure in /dev/vinum:

brwx------  1 root  wheel   25, 0x40000001 Apr 13 16:46 Control
brwx------  1 root  wheel   25, 0x40000002 Apr 13 16:46 control
brwx------  1 root  wheel   25, 0x40000000 Apr 13 16:46 controld
drwxr-xr-x  2 root  wheel       512 Apr 13 16:46 drive
drwxr-xr-x  2 root  wheel       512 Apr 13 16:46 plex
crwxr-xr--  1 root  wheel   91,   2 Apr 13 16:46 rs64
drwxr-xr-x  2 root  wheel       512 Apr 13 16:46 rsd
drwxr-xr-x  2 root  wheel       512 Apr 13 16:46 rvol
brwxr-xr--  1 root  wheel   25,   2 Apr 13 16:46 s64
drwxr-xr-x  2 root  wheel       512 Apr 13 16:46 sd
drwxr-xr-x  3 root  wheel       512 Apr 13 16:46 vol

/dev/vinum/drive:
total 0
lrwxr-xr-x  1 root  wheel  9 Apr 13 16:46 drive1 -> /dev/sd1h
lrwxr-xr-x  1 root  wheel  9 Apr 13 16:46 drive2 -> /dev/sd2h
lrwxr-xr-x  1 root  wheel  9 Apr 13 16:46 drive3 -> /dev/sd3h
lrwxr-xr-x  1 root  wheel  9 Apr 13 16:46 drive4 -> /dev/sd4h

/dev/vinum/plex:
total 0
brwxr-xr--  1 root  wheel   25, 0x10000002 Apr 13 16:46 s64.p0

/dev/vinum/rsd:
total 0
crwxr-xr--  1 root  wheel   91, 0x20000002 Apr 13 16:46 s64.p0.s0
crwxr-xr--  1 root  wheel   91, 0x20100002 Apr 13 16:46 s64.p0.s1
crwxr-xr--  1 root  wheel   91, 0x20200002 Apr 13 16:46 s64.p0.s2
crwxr-xr--  1 root  wheel   91, 0x20300002 Apr 13 16:46 s64.p0.s3

/dev/vinum/rvol:
total 0
crwxr-xr--  1 root  wheel   91,   2 Apr 13 16:46 s64

/dev/vinum/sd:
total 0
brwxr-xr--  1 root  wheel   25, 0x20000002 Apr 13 16:46 s64.p0.s0
brwxr-xr--  1 root  wheel   25, 0x20100002 Apr 13 16:46 s64.p0.s1
brwxr-xr--  1 root  wheel   25, 0x20200002 Apr 13 16:46 s64.p0.s2
brwxr-xr--  1 root  wheel   25, 0x20300002 Apr 13 16:46 s64.p0.s3

/dev/vinum/vol:
total 1
brwxr-xr--  1 root  wheel   25,   2 Apr 13 16:46 s64
drwxr-xr-x  3 root  wheel       512 Apr 13 16:46 s64.plex

/dev/vinum/vol/s64.plex:
total 1
brwxr-xr--  1 root  wheel   25, 0x10000002 Apr 13 16:46 s64.p0
drwxr-xr-x  2 root  wheel       512 Apr 13 16:46 s64.p0.sd

/dev/vinum/vol/s64.plex/s64.p0.sd:
total 0
brwxr-xr--  1 root  wheel   25, 0x20000002 Apr 13 16:46 s64.p0.s0
brwxr-xr--  1 root  wheel   25, 0x20100002 Apr 13 16:46 s64.p0.s1
brwxr-xr--  1 root  wheel   25, 0x20200002 Apr 13 16:46 s64.p0.s2
brwxr-xr--  1 root  wheel   25, 0x20300002 Apr 13 16:46 s64.p0.s3

Although it is recommended that plexes and subdisks should not be allocated specific names, Vinum drives must be named. This makes it possible to move a drive to a different location and still recognize it automatically. Drive names may be up to 32 characters long.

Creating file systems

Volumes appear to the system to be identical to disks, with one exception. Unlike UNIX drives, Vinum does not partition volumes, which thus do not contain a partition table. This has required modification to some disk utilities, notably newfs, which previously tried to interpret the last letter of a Vinum volume name as a partition identifier. For example, a disk drive may have a name like /dev/wd0a or /dev/da2h. These names represent the first partition (a) on the first (0) IDE disk (wd) and the eight partition (h) on the third (2) SCSI disk (da) respectively. By contrast, a Vinum volume may be called /dev/vinum/concat.

Normally, newfs(8) interprets the name of the disk and complains if it cannot understand it. For example:

# newfs /dev/vinum/concat
newfs: /dev/vinum/concat: can't figure out file system partition

In order to create a file system on this volume, use the -v option to newfs(8):

# newfs -v /dev/vinum/concat

Following Sections

Startup
Performance issues
The implementation
Driver structure
Availability
Future directions
References