AIX中的VG类型，以及如何改变VG

VG type	Maximum PVs	Maximum LVs	Maximum PPs per VG	Maximum PP size
Normal VG	32	256	32,512 (1016 * 32)	1 GB
Big VG	128	512	130,048 (1016 * 128)	1 GB
Scalable VG	1024	4096	2,097,152	128 GB

首先如何查看VG是什么类型呢？
通过如下方法

例如：hdisk2 属于 datavg
那么执行#readvgda hdisk2|grep type
..... readvgda_type: smallvg
vgtype: 0
可以发现datavg是normal VG。

维护过程中用的最多的是，如何平衡一个VG中的PP与PV，LV的数量。
如何在不改变VG类型的情况下，改变VG中的最大PP数量呢？
可以通过修改factor因子，来平衡PP和PV的数量
例如：
# lsvg datavg
VOLUME GROUP: datavg VG IDENTIFIER: 00f7433800004c000000013808c3ac8d
VG STATE: active PP SIZE: 4 megabyte(s)
VG PERMISSION: read/write TOTAL PPs: 48 (192 megabytes)
MAX LVs: 256 FREE PPs: 10 (40 megabytes)
LVs: 3 USED PPs: 38 (152 megabytes)
OPEN LVs: 2 QUORUM: 1 (Disabled)
TOTAL PVs: 2 VG DESCRIPTORS: 3
STALE PVs: 0 STALE PPs: 0
ACTIVE PVs: 2 AUTO ON: no
Concurrent: Enhanced-Capable Auto-Concurrent: Disabled
VG Mode: Non-Concurrent
MAX PPs per VG: 32512
MAX PPs per PV: 1016 MAX PVs: 32
LTG size (Dynamic): 128 kilobyte(s) AUTO SYNC: no
HOT SPARE: no BB POLICY: relocatable
PV RESTRICTION: none INFINITE RETRY: no
# lsvg -p datavg
datavg:
PV_NAME PV STATE TOTAL PPs FREE PPs FREE DISTRIBUTION
hdisk2 active 24 5 04..00..00..00..01
hdisk5 active 24 5 04..00..00..00..01
# readvgda hdisk2|grep type
..... readvgda_type: smallvg
vgtype: 0
# set -o vi
# readvgda hdisk2|grep factor
factor: 1
# chvg -t 2 datavg 更改factor 为2
0516-1164 chvg: Volume group datavg changed. With given characteristics datavg
can include up to 16 physical volumes with 2032 physical partitions each.
# lsvg datavg
VOLUME GROUP: datavg VG IDENTIFIER: 00f7433800004c000000013808c3ac8d
VG STATE: active PP SIZE: 4 megabyte(s)
VG PERMISSION: read/write TOTAL PPs: 48 (192 megabytes)
MAX LVs: 256 FREE PPs: 10 (40 megabytes)
LVs: 3 USED PPs: 38 (152 megabytes)
OPEN LVs: 2 QUORUM: 1 (Disabled)
TOTAL PVs: 2 VG DESCRIPTORS: 3
STALE PVs: 0 STALE PPs: 0
ACTIVE PVs: 2 AUTO ON: no
Concurrent: Enhanced-Capable Auto-Concurrent: Disabled
VG Mode: Non-Concurrent
MAX PPs per VG: 32512
MAX PPs per PV: 2032 MAX PVs: 16
LTG size (Dynamic): 128 kilobyte(s) AUTO SYNC: no
HOT SPARE: no BB POLICY: relocatable
PV RESTRICTION: none INFINITE RETRY: no
#
# readvgda hdisk2|grep factor
factor: 2

还有一种方法就是改变VG类型，来增大PP,PV,LV的最大数量
# chvg -B mndhb_vg_01 改变VG为Big VG类型
0516-1164 chvg: Volume group mndhb_vg_01 changed. With given characteristics mndhb_vg_01
can include up to 64 physical volumes with 2032 physical partitions each.
# lsvg mndhb_vg_01
VOLUME GROUP: mndhb_vg_01 VG IDENTIFIER: 00f7433800004c000000013808c3ac8d
VG STATE: active PP SIZE: 4 megabyte(s)
VG PERMISSION: read/write TOTAL PPs: 44 (176 megabytes)
MAX LVs: 512 FREE PPs: 6 (24 megabytes)
LVs: 3 USED PPs: 38 (152 megabytes)
OPEN LVs: 2 QUORUM: 1 (Disabled)
TOTAL PVs: 2 VG DESCRIPTORS: 3
STALE PVs: 0 STALE PPs: 0
ACTIVE PVs: 2 AUTO ON: no
Concurrent: Enhanced-Capable Auto-Concurrent: Disabled
VG Mode: Non-Concurrent
MAX PPs per VG: 130048
MAX PPs per PV: 2032 MAX PVs: 64
LTG size (Dynamic): 128 kilobyte(s) AUTO SYNC: no
HOT SPARE: no BB POLICY: relocatable
PV RESTRICTION: none INFINITE RETRY: no

# readvgda hdisk2|grep type
..... readvgda_type: bigvg
vgtype: 1

注意如果将VG类型改为Scalable VG时，需要首先varyoffvg
#varyoffvg datavg
#chvg -G datavg
#varyonvg datavg
建议在新部署系统的时候，建立VG时，选择Scalable VG，这样可以消除512 byte logical volume control block (LVCB) offset to affect aligned writes (often found on systems using raw LVs with Oracle databases)的限制

特别提示：进行chvg -B和chvg -G的操作的时候，vg中每个pv必须有足够的空余free空间，来存放vgda的变更。