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As I understand LVM, for mirrored disks (like rootvg below), only 1016 PP's
are tracked for tracking mirror 'staleness'. However, in the rootvg example
below, even though there are more than 1016 PPs in the physical volume, only
622 are actually used. Since what's used is less than 1016, will the LVM
still be able to reliably track PP 'staleness' (until I actually allocate
*over* 1016 of these PPs)?

VOLUME GROUP: rootvg VG IDENTIFIER: 000ac8bf19603fe8
VG STATE: active PP SIZE: 32 megabyte(s)
VG PERMISSION: read/write TOTAL PPs: 1084 (34688
megabytes)
MAX LVs: 256 FREE PPs: 462 (14784
megabytes)
LVs: 9 USED PPs: 622 (19904
megabytes)
OPEN LVs: 8 QUORUM: 1
TOTAL PVs: 2 VG DESCRIPTORS: 3
STALE PVs: 0 STALE PPs: 0
ACTIVE PVs: 2 AUTO ON: yes
MAX PPs per PV: 1016 MAX PVs: 32

Likewise, the datavg volume group is not mirrored, but is a RAID5 array off
a RAID5 hardware controller. Since this is not mirrored, is the 1016 PP
limitation violation below still a potential problem?
If so, what would the symptoms be, as there's no mirror to go 'stale'.

VOLUME GROUP: datavg VG IDENTIFIER: 000ac8bf7362eadb
VG STATE: active PP SIZE: 128 megabyte(s)
VG PERMISSION: read/write TOTAL PPs: 1084 (138752
megabytes)
MAX LVs: 256 FREE PPs: 0 (0 megabytes)
LVs: 4 USED PPs: 1084 (138752
megabytes)
OPEN LVs: 4 QUORUM: 2
TOTAL PVs: 2 VG DESCRIPTORS: 3
STALE PVs: 0 STALE PPs: 0
ACTIVE PVs: 2 AUTO ON: yes
MAX PPs per PV: 1016 MAX PVs: 32

Thanks for the clarification.
Ken

On Tue, 1 Feb 2005 18:25:06 -0800, "KenA" <kabrahamsen@comcast.net>
wrote:

>As I understand LVM, for mirrored disks (like rootvg below), only 1016 PP's
>are tracked for tracking mirror 'staleness'. However, in the rootvg example
>below, even though there are more than 1016 PPs in the physical volume, only
>622 are actually used. Since what's used is less than 1016, will the LVM
>still be able to reliably track PP 'staleness' (until I actually allocate
>*over* 1016 of these PPs)?
>
>VOLUME GROUP: rootvg VG IDENTIFIER: 000ac8bf19603fe8
>VG STATE: active PP SIZE: 32 megabyte(s)
>VG PERMISSION: read/write TOTAL PPs: 1084 (34688
>megabytes)
>MAX LVs: 256 FREE PPs: 462 (14784
>megabytes)
>LVs: 9 USED PPs: 622 (19904
>megabytes)
>OPEN LVs: 8 QUORUM: 1
>TOTAL PVs: 2 VG DESCRIPTORS: 3
>STALE PVs: 0 STALE PPs: 0
>ACTIVE PVs: 2 AUTO ON: yes
>MAX PPs per PV: 1016 MAX PVs: 32
>
>Likewise, the datavg volume group is not mirrored, but is a RAID5 array off
>a RAID5 hardware controller. Since this is not mirrored, is the 1016 PP
>limitation violation below still a potential problem?
>If so, what would the symptoms be, as there's no mirror to go 'stale'.
>
>VOLUME GROUP: datavg VG IDENTIFIER: 000ac8bf7362eadb
>VG STATE: active PP SIZE: 128 megabyte(s)
>VG PERMISSION: read/write TOTAL PPs: 1084 (138752
>megabytes)
>MAX LVs: 256 FREE PPs: 0 (0 megabytes)
>LVs: 4 USED PPs: 1084 (138752
>megabytes)
>OPEN LVs: 4 QUORUM: 2
>TOTAL PVs: 2 VG DESCRIPTORS: 3
>STALE PVs: 0 STALE PPs: 0
>ACTIVE PVs: 2 AUTO ON: yes
>MAX PPs per PV: 1016 MAX PVs: 32
>
>Thanks for the clarification.
>Ken
>


AIX does not mirror physical disks. AIX mirrors logical volumes. If
all the logical volumes in your rootvg are mirrored, AIX will only
mirror those PPs that belong to logical volumes. The PPs that are not
allocated are not mirrored or used in any way. There is not limit to
how many PPs in a VG AIX can mirror, AIX can mirror and "track
staleness" of ALL the PPs in a volume group.

The 1016 PP limit is for a single physical disk, not for a VG. In
both your rootvg and datavg you have 1084 PPs spread across 2 PVs, so
there are presumably 542 PPs per PV, which is well within the 1016
limit. AIX will not let you add a physical volume to a volume group
if the size of the physical volume divided by the volume group's PP
size would require more than 1016 PPs to encompass the physical
volume. Actually, I think it might let you but it will warn you that
you're wasting space because you can't use more than 1016 PPs.
Adjusting the PP size at volume group creation time is how you prepare
yourself for using larger physical drives. Your datavg has a PP size
of 128M so you can use physical drives (or RAID groups) up to 127GB
without troubles. In your rootvg the PP size is 32M so you can use up
to 31.75GB disks.