asmca创建磁盘时发现不了磁盘，11.2.0.3却正常。磁盘属性这些都正常。
# bootinfo -s hdisk10
1048576

磁盘大小为1T。

检查metalink，发现11.2.0.2有如下bug：
SQL> create diskgroup datadg external redundancy disk '/dev/rhdisk26';

create diskgroup datadg external redundancy disk '/dev/rhdisk26'

*

ERROR at line 1:

ORA-15018: diskgroup cannot be created

ORA-15099: disk '/dev/rhdisk26' is larger than maximum size of 2097152 MBs

# bootinfo -s hdisk10
1048576

bug :
Bug 10072750 AIX: ASM sees 1 TB disks as larger than their actual size (ORA-15099) This note gives a brief overview of bug 10072750.
The content was last updated on: 28-JUN-2013
Click here for details of each of the sections below.

Affects:

Product (Component)	Oracle Server (Rdbms)
Range of versions believed to be affected	Versions BELOW 12.1
Versions confirmed as being affected	11.2.0.2 11.2.0.1
Platforms affected	IBM AIX Power Based Systems (64bit)

Fixed:

This issue is fixed in

12.1.0.1 (Base Release) 11.2.0.3 (Server Patch Set)

Symptoms:	Related To:
ORA-15099	Large File / Memory Issues (Eg: 2Gb) Automatic Storage Management (ASM)

Description

When the disk size is greater than 1 TB then the disk size 
for ASM is thought to be more than the actual size.
 
Rediscovery Notes:
 When the size of the disk is greater than 1 TB and there is problem
 with create diskgroup command, with error ORA-15099, there is a
 possibility that this bug is hit.
 
Workaround
 While creating the diskgroup, manually specify the disk size

解决办法:创建磁盘组时，手工指定大小：

create diskgroup datadg external redundancy disk '/dev/rhdisk26' size 1048575m;