iSCSI 使用的 TCP 知名端口号是 3260。

Initiator 指的是 iSCSI 的客户端。
Target 指的是 iSCSI 的服务器端。

Open-iSCSI 是 Linux 上常见的一个开源 iSCSI initiator 实现。而 iscsiadm 则是 Open-iSCSI 的管理工具。比如 iscsiadm –mode node 命令可以列出所有的节点记录：

# iscsiadm -m node
130.35.224.163:3260,2 iqn.1986-03.com.sun:02:6794049e-b92f-4b33-cb1c-8f69c8316449

这里可以看到 target 的 IP 地址是 130.35.224.163，通过 nslookup 可以查到这个 target 其实是同一个网络上的一个 NAS。这里 target 采用的命名方式是 IQN (iSCSI Qualified Name)。

References
RFC 3720
RFC 3721

最近尝试了一下将Oracle Clusterware 11gR1的OCR和VD放在OCFS2上，这里记录一下OCFS2的安装过程。

首先是确定所使用的Linux的发行版本（distribution），内核版本（version）和风格（flavor），处理器架构：

# cat /etc/redhat-release
Enterprise Linux Enterprise Linux AS release 4 (October Update 5)

# uname -r
2.6.9-67.0.4.0.2.ELsmp

# uname -p
i686

可以看到这里我使用的是Oracle Enterprise Linux 4u5（可以认为是等同于Red Hat Enterprise Linux 4u5），内核版本是2.6.9-67.0.4.0.2，内核风格是smp，处理器架构是i686（也就是x86）。

接下来按照上面的信息去下载相应的OCFS2和OCFS2 Tools（包括ocfs2-tools和ocfs2console）的RPM包。

# wget -c http://oss.oracle.com/projects/ocfs2/dist/files/RedHat/RHEL4/i386/1.2.9-1/2.6.9-67.0.4.EL/ocfs2-2.6.9-67.0.4.ELsmp-1.2.9-1.el4.i686.rpm
# wget -c http://oss.oracle.com/projects/ocfs2-tools/dist/files/RedHat/RHEL4/i386/1.2.7-1/ocfs2-tools-1.2.7-1.el4.i386.rpm
# wget -c http://oss.oracle.com/projects/ocfs2-tools/dist/files/RedHat/RHEL4/i386/1.2.7-1/ocfs2console-1.2.7-1.el4.i386.rpm

删除掉现有的老版本的OCFS2相关RPM包：

# rpm -qa | grep ocfs | xargs rpm -e

依次安装刚刚下载的3个RPM：

# rpm -ivh ocfs2-tools-1.2.7-1.el4.i386.rpm
# rpm -ivh ocfs2console-1.2.7-1.el4.i386.rpm
# rpm -ivh --nodeps ocfs2-2.6.9-67.0.4.ELsmp-1.2.9-1.el4.i686.rpm

注意安装OCFS2 RPM时需要加上“–nodeps”选项。

这里还有一个问题，上面安装的OCFS2 RPM的内核版本（2.6.9-67.0.4）与我所使用的Linux的内核版本（2.6.9-67.0.4.0.2）并不完全一致，所以还需要进行下面的额外工作：

# cp -r /lib/modules/2.6.9-67.0.4.ELsmp/kernel/fs/* /lib/modules/2.6.9-67.0.4.0.2.ELsmp/kernel/fs

至此，OCFS2的安装已经完成。

raw -qa

命令来查询当前已经存在的绑定。

Use  the /etc/sysconfig/rawdevices file to define the set of raw device mappings automatically created during the system startup sequence.

在/etc/sysconfig/rawdevices中，注意裸设备对应的块设备如果是SATA或者iSCSI，则应该使用/dev/disk/by-id中的链接来进行指定。

如何确定裸设备对应的块设备？以裸设备/dev/raw/raw57为例：

# ls -l /dev/raw/raw57
crw-rw—-  1 root disk 162, 57 Jul 31 02:02 /dev/raw/raw57

# raw -qa | grep raw57
/dev/raw/raw57: bound to major 65, minor 233

# ls -l /dev | grep 65 | grep 233
brwxrwxrwx  1 root    disk    65, 233 Jul 31 02:01 sdae9

从而知道裸设备/dev/raw/raw57是绑定到了/dev/sdae9这个块设备。

A VM disk typically includes a public region (allocated storage) and a private region where Volume Manager internal configuration information is stored.

A disk group is a collection of VM disks that share a common configuration.

A disk group configuration is a set of records with detailed information about related Volume Manager objects, their attributes, and their connections.

Volumes are created within a disk group. A given volume must be configured from disks in the same disk group.

A subdisk is a set of contiguous disk blocks. A block is a unit of space on the disk. Volume Manager allocates disk space using subdisks.

The Volume Manager uses subdisks to build virtual objects called plexes. A plex consists of one or more subdisks located on one or more physical disks.

A volume is a virtual disk device that appears to applications, databases, and file systems as a physical disk, but does not have the physical limitations of a physical disk device.

A volume consists of one or more plexes, each holding a copy of the selected data in the volume. Due to its virtual nature, a volume is not restricted to a particular disk or a specific area of disk.

A volume can consist of up to 32 plexes, each of which consists of one or more subdisks.

OCFS2

Open-iSCSI

A discussion on OCFS, OCFS2, ASM, RAW