关于oracle11gASM使用时要注意的点
1. 配置最少2个data group （datagroup 存放数据文件； fra datagroup 作为闪回区方归档 ，备份等）主要考虑的是io 性能问题
2. oracle 官方文档建议每个dg 最少4块盘且大小，性能一样。否者io 将会受限于速度最慢的那个盘
3. 硬件raid 条带大小取2的幂，且要<= asm au size
4.支持存储：
Disk Partition
A disk partition can be the entire disk drive or a section of a disk drive. 注意使用磁盘分区不能后分区表，因为分区表会被覆盖。
Logical
Unit Number (LUN)：
A LUN is a disk presented to a computer system by a storage array. oracle建议使用硬raid
Logical
Volume：
A logical volume is supported in less complicated configurations where a logical volume is mapped to a LUN, or a logical volume uses disks or raw partitions。oracle 不太建议使用逻辑卷，因为他们和oracle asm 有功能（ mirroring）上的重复
Network
File System (NFS)：
An Oracle ASM disk group can be created from NFS files, including Oracle Direct NFS (dNFS), as well as whole disks, partitions, and LUNs.
Direct NFS can be used to store data files, but is not supported for Oracle Clusterware files.