ASM二 存储

ASM可用的磁盘类型：

1.磁盘或磁盘分区。但是不能使用有分区表的磁盘分区(However, the Oracle ASM disk cannot be in a partition that includes the partition table because the partition table would be overwritten.)

2.LUN（Logical Unit Number ） 逻辑单元，如RAID，通常使用RAID0+1或RAID 5.

3.LV（Logical Volume） 逻辑卷。

4.NFS（Network File System）网络文件系统。NFS只能用于保存数据文件，而不能保存集群文件(Oracle Clusterware files). 

准备ASM磁盘：

1.确定磁盘路径，在linux下，一般是/dev/device_name

2.修改磁盘拥有者和权限，如拥有者grid:asmadmin,权限read/write

此外，配置正确的ASM_DISKSTRING  参数。

一般情况下，磁盘的所有者应该与ORACLE二进制文件的所有者在同一个组，应该是ASM实例的OSDBA组。

存储准备的建议

1. Configure two disk groups, one for data and the other for the fast recovery area. 使用两个磁盘组，一个存储数据，一个做FRA
   
2. A minimum of four LUNs (Oracle ASM disks) of equal size and performance is recommended for each disk group.至少4个容量和性能相同的ASM磁盘
   
3. Ensure that all Oracle ASM disks in a disk group have similar storage performance and availability characteristics. In storage configurations with mixed speed drives, such as 10K and 15K RPM, I/O performance is constrained by the slowest speed drive.同一个磁盘组的磁盘拥有相同的性能，磁盘组的性能等于磁盘组中性能最差的磁盘。
   
4. Oracle ASM data distribution policy is capacity-based. Ensure that Oracle ASM disks in a disk group have the same capacity to maintain balance.磁盘组的磁盘拥有相同的性能。
   
5. Create external redundancy disk groups when using high-end storage arrays。在使用了高端存储后使用外部冗余。
   
6. Minimize I/O contention between Oracle ASM disks and other applications by dedicating disks in Oracle ASM disk groups.减少ASM磁盘争用，不要让其它程序使用ASM磁盘组所在的磁盘。
   
7. Choose a hardware RAID stripe size that is a power of 2 and less than or equal to the size of the Oracle ASM allocation unit. RAID的条带化单元应该是2的倍数，并且<＝ASM的AU大小。
   
8. For Linux, use the Oracle ASMLib feature to provide consistent device naming and permission persistency.使用始终使用ASMLIB来管理磁盘的名称和权限。