0516-404 allocp: This system cannot fulfill the allocation request

When increasing logical volumes or file systems, the error “0516-404 allocp: This system cannot fulfill the allocation request” often occurs. Many AIX administrators are at first a little at a loss as to what the cause of the problem is: is it due to max LPs or upper bound, the chosen strictness or does the problem have completely different causes. Unfortunately, the error message is only generic and does not say what the real problem is. A good way to get to the bottom of the problem is the alog lvmt, in which all LVM actions, especially the low-level commands, including error messages are logged.

Our article Troubleshooting problems with extendlv and file system extension uses a series of examples to show how the cause of the problem can be found in many cases.

0516-787 extendlv: Maximum allocation for logical volume lv01 is 512

If the following message occurs while expanding a logical volume or file system:

# chfs -a size=+5G /fs01
0516-787 extendlv: Maximum allocation for logical volume fslv01
        is 512.

Then the cause is a limitation of the logical volume. The size of a logical volume is limited by the maximum number of LPs (logical partitions) that can be allocated for the logical volume. The error message says exactly that and even gives the current value for the maximum number of LPs. This is a changeable attribute of the logical volume and can be displayed with the lslv command:

$ lslv fslv01
...MAX LPs:            512                    PP SIZE:        8 megabyte(s)

The attribute can be changed with the command chlv:

# chlv -x 768 fslv01

With a PP (Physical Partition) size of 8 MB, 768 PPs are sufficient for exactly 6 GB. Of course, you could consider the next expansion and set the value accordingly higher.

If there are enough 0516-787 extendlv: Maximum allocation for logical volumes free in the underlying volume group and no other limits are exceeded, the file system or logical volume should now be able to be expanded:

# chfs -a size=+5G /fs01
Filesystem size changed to 12582912
Inlinelog size changed to 24 MB.

Correcting “wrong” LVM mirroring

Mirrored logical volume from practice

In Part III of our article series “AIX LVM: Mechanics of migratepv” we show how incorrect mirroring of logical volumes can be corrected online. All that is required is the migratelp and migratepv commands and a good understanding of how these commands work.

Here are the links to the articles in the series:

AIX LVM: Mechanics of migratepv (Part I)

AIX LVM: Mechanics of migratepv (Part II)

AIX LVM: Mechanics of migratepv (Part III)

Error: Mirror pools must be defined

The following error message occurred while creating a mirrored logical volume:

# mklv -c 2 -t jfs2 datavg01 10
0516-1814 lcreatelv: Mirror pools must be defined for each copy when strict mirror
        pools are enabled.
0516-822 mklv: Unable to create logical volume.

The reason for this is that the mirror pool strictness is set for the volume group. The article Mirror Pools: Understanding Mirror Pool Strictness examines and explains this in more detail.

New Article Introduction to Mirror Pools

Many IT environments operate their systems in more than one data center. In order not to have any data loss in the event of a failure of an entire data center, the data is mirrored between 2 or more data centers. The mirroring can be realized by the storage (storage based mirroring) or by a volume manager (LVM in the case of AIX) on the server (host based mirroring). In the article Mirror Pools: An Introduction we look at mirroring using AIX Logical Volume Manager and Mirror Pools. The aim is to show how the correct mirroring of logical volumes can be implemented with the help of mirror pools. In larger environments with many physical volumes, maintaining correct mirroring without mirror pools is difficult and a challenge for the administrator.