VxVM Disk Headers

Veritas Disk Headers

When a device is initialized or encapsulated with Veritas Volume Manager, a disk header is written to the device's private region. The disk header contains a diskid to uniquely identify the device, a disk group identifier to indicate which disk group the device is associated with, a set of flags to indicate the status and intended use (e.g., hot spare) of the device, and a hostid to indicate which host (if any) has the device imported. The disk header can be printed by passing the Veritas device name to vxdisk(1m)'s "list" option:

$ vxdisk list c1t1d0

Device: c1t1d0s2
devicetag: c1t1d0
type: auto
hostid: pooh
disk: name=c1t1d0 id=1123602295.10.pooh
group: name=oradg id=1123603158.13.pooh
info: format=cdsdisk,privoffset=256,pubslice=2,privslice=2
flags: online ready private autoconfig autoimport imported
pubpaths: block=/dev/vx/dmp/c1t1d0s2 char=/dev/vx/rdmp/c1t1d0s2
version: 3.1
iosize: min=512 (bytes) max=2048 (blocks)
public: slice=2 offset=2304 len=35365968 disk_offset=0
private: slice=2 offset=256 len=2048 disk_offset=0
update: time=1123603160 seqno=0.6
ssb: actual_seqno=0.0
headers: 0 240
configs: count=1 len=1280
logs: count=1 len=192
Defined regions:
config priv 000048-000239[000192]: copy=01 offset=000000 enabled
config priv 000256-001343[001088]: copy=01 offset=000192 enabled
log priv 001344-001535[000192]: copy=01 offset=000000 enabled
lockrgn priv 001536-001679[000144]: part=00 offset=000000
Multipathing information:
numpaths: 1
c1t1d0s2 state=enabled

Due to the critical nature of the configuration information stored in the disk headers, it is important to periodically back up this information. As I will discuss in the section Configuration Backups, Veritas introduced new features in Veritas Volume Manager 4.X to ease the backup process.