Logical volume management

[Dan Nelson]

In the last episode (Nov 18), Brian Candler said:
> Vinum's manpage makes my head spin. I was wondering if anyone had
> considered implementing something a bit more straightforward and also
> more dynamic.
> 
> Suppose you:
> 
> (1) Divide all your disks up-front into equal sized chunks, say 4MB.
> 
> (2) Use an indirection table to map each volume into an arbitary set of
>     these chunks across all available disks.
> 
> (3) Store the indirection table at the end of a partition, as other
>     GEOM modules do for their metadata, and cache it in RAM.
> 
> (e.g. a 160GB drive, divided into 4MB blocks, each of which has a
> 32-bit indirection table entry, would require only 160KB of
> indirection table)

AIX does something similar in its volume manager.  A volume group
consists of a number of disks, split into equal-sized partitions (256MB
is the default I think).  Logical volumes reside in the volume group,
and are composed of multiple partitions.  Each LV can have its own
raid/mirror characteristics separate from others, and can be grown,
mirrored, or otherwise modified online.

http://publib.boulder.ibm.com/infocenter/pseries/topic/com.ibm.aix.doc/aixbman/admnconc/logical_vol.htm
http://publib.boulder.ibm.com/infocenter/pseries/topic/com.ibm.aix.doc/aixbman/prftungd/diskperf.htm
 
-- 
	Dan Nelson
	dnelson at allantgroup.com