Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

Contents
Chapter 1 Understanding Veritas Volume Manager
VxVM and the operating system ..............................................................................19
How data is stored ............................................................................................19
How VxVM handles storage management ...............................................................20
Physical objects—physical disks ......................................................................20
Virtual objects ...................................................................................................25
Volume layouts in VxVM .........................................................................................34
Implementation of non-layered volumes ..........................................................34
Implementation of layered volumes .................................................................34
Layout methods ................................................................................................35
Concatenation and spanning .............................................................................35
Striping (RAID-0) .............................................................................................38
Mirroring (RAID-1) ..........................................................................................42
Striping plus mirroring (mirrored-stripe or RAID-0+1) ...................................42
Mirroring plus striping (striped-mirror, RAID-1+0 or RAID-10) ....................43
RAID-5 (striping with parity) ...........................................................................45
Layered volumes ...............................................................................................51
Online relayout .........................................................................................................54
How online relayout works ...............................................................................54
Limitations of online relayout ..........................................................................57
Transformation characteristics ..........................................................................58
Transformations and volume length .................................................................58
Volume resynchronization ........................................................................................59
Dirty flags .........................................................................................................59
Resynchronization process ...............................................................................59
Dirty region logging ..................................................................................................60
Dirty region logs ...............................................................................................60
Log subdisks and plexes ...................................................................................61
Sequential DRL ................................................................................................61
SmartSync recovery accelerator .......................................................................62
Volume snapshots .....................................................................................................63
Comparison of snapshot features ......................................................................65
FastResync ................................................................................................................66
FastResync enhancements ................................................................................67
Non-persistent FastResync ...............................................................................67
Persistent FastResync .......................................................................................68