上一篇文章《使用_asm_allow_only_raw_disks实现普通文件做asm disk》中已经介绍使用_asm_allow_only_raw_disks参数使得oracle asm可以使用文件作为asm disk,这篇文章介绍在linux中还可以通过losetup来实现文件系统模拟磁盘实现使用文件系统做asm disk的效果
通过dd构造文件

[oracle@xifenfei ~]$ mkdir /u01/oracle/oradata/asmdisk
[oracle@xifenfei ~]$ dd if=/dev/zero of=/u01/oracle/oradata/asmdisk/xifenfei01.dd bs=10240k count=100
100+0 records in
100+0 records out
1048576000 bytes (1.0 GB) copied, 21.9158 seconds, 47.8 MB/s
[oracle@xifenfei ~]$ dd if=/dev/zero of=/u01/oracle/oradata/asmdisk/xifenfei02.dd bs=10240k count=100
100+0 records in
100+0 records out
1048576000 bytes (1.0 GB) copied, 22.392 seconds, 46.8 MB/s
[oracle@xifenfei ~]$ ls -lh /u01/oracle/oradata/asmdisk/
total 3.0G
-rw-r--r-- 1 oracle oinstall 1000M Feb 27 22:58 xifenfei01.dd
-rw-r--r-- 1 oracle oinstall 1000M Feb 27 23:00 xifenfei02.dd

使用losetup模拟磁盘

[root@xifenfei asmdisk]# ls -l /dev/lo
log    loop0  loop1  loop2  loop3  loop4  loop5  loop6  loop7  
[root@xifenfei asmdisk]# losetup /dev/loop1 xifenfei01.dd 
[root@xifenfei asmdisk]# losetup /dev/loop2 xifenfei02.dd 

使用raw实现磁盘转换为裸设备

[root@xifenfei asmdisk]# raw  /dev/raw/raw10 /dev/loop1 
/dev/raw/raw10: bound to major 7, minor 1
[root@xifenfei asmdisk]# raw  /dev/raw/raw11 /dev/loop2 
/dev/raw/raw11: bound to major 7, minor 2
[root@xifenfei asmdisk]# ls -l /dev/raw/raw1[0-1]
crw------- 1 root root 162, 10 Feb 27 23:16 /dev/raw/raw10
crw------- 1 root root 162, 11 Feb 27 23:16 /dev/raw/raw11
[root@xifenfei asmdisk]# chown oracle.dba /dev/raw/raw1[0-1]
[root@xifenfei asmdisk]# ls -l /dev/raw/raw1[0-1]
crw------- 1 oracle dba 162, 10 Feb 27 23:16 /dev/raw/raw10
crw------- 1 oracle dba 162, 11 Feb 27 23:16 /dev/raw/raw11

创建磁盘组

[oracle@xifenfei ~]$ export ORACLE_SID=+ASM
[oracle@xifenfei ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.4.0 - Production on Thu Feb 27 23:19:28 2014

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options


SQL>  create diskgroup xff external redundancy disk '/dev/raw/raw10','/dev/raw/raw11';

Diskgroup created.

SQL> select group_number,name from v$asm_diskgroup;

GROUP_NUMBER NAME
------------ ------------------------------------------------------------
           1 DATA
           2 XFF

SQL> select path,TOTAL_MB from v$asm_disk where group_number=2;

PATH                   TOTAL_MB
-------------------- ----------
/dev/raw/raw11             1000
/dev/raw/raw10             1000

通过kfed验证asm disk是数据文件

[oracle@xifenfei tmp]$ kfed read /dev/raw/raw10|grep XFF
kfdhdb.dskname:                XFF_0000 ; 0x028: length=8
kfdhdb.grpname:                     XFF ; 0x048: length=3
kfdhdb.fgname:                 XFF_0000 ; 0x068: length=8
[oracle@xifenfei tmp]$ kfed read /dev/raw/raw11|grep XFF
kfdhdb.dskname:                XFF_0001 ; 0x028: length=8
kfdhdb.grpname:                     XFF ; 0x048: length=3
kfdhdb.fgname:                 XFF_0001 ; 0x068: length=8
[oracle@xifenfei tmp]$ kfed read /u01/oracle/oradata/asmdisk/xifenfei01.dd |grep XFF
kfdhdb.dskname:                XFF_0000 ; 0x028: length=8
kfdhdb.grpname:                     XFF ; 0x048: length=3
kfdhdb.fgname:                 XFF_0000 ; 0x068: length=8
[oracle@xifenfei tmp]$ kfed read /u01/oracle/oradata/asmdisk/xifenfei02.dd |grep XFF
kfdhdb.dskname:                XFF_0001 ; 0x028: length=8
kfdhdb.grpname:                     XFF ; 0x048: length=3
kfdhdb.fgname:                 XFF_0001 ; 0x068: length=8

通过kfed命令,确定asm本质是用了dd出来的数据文件做asm disk.