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[#]: collector: (lujun9972)
[#]: translator: (geekpi)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
[#]: subject: (How to Scan/Detect New LUNs and SCSI Disks on Linux)
[#]: via: (https://www.2daygeek.com/scan-detect-luns-scsi-disks-on-redhat-centos-oracle-linux/)
[#]: author: (Magesh Maruthamuthu https://www.2daygeek.com/author/magesh/)
How to Scan/Detect New LUNs and SCSI Disks on Linux
======
When the Linux system has connected to the SAN (Storage Area Network) you need to rescan the iSCSI service to discover new LUNs.
To do so, you must provide the WWN number of the Linux host and required LUN size to the storage team.
The following article will help you [**find the WWN number of a Linux host**][1].
Once the storage team has mapped the LUNs with the given Linux host, they will provide you with the new LUN details.
LUN in storage terms is referred to as serial-hex of LUN.
You need to scan the SCSI host to find new LUNs assigned by the storage team.
This can be done in two ways, scan each scsi host device or run the “rescan-scsi-bus.sh” script to detect new disks.
After scanning they can be found under the “/dev/disk/by-id” directory.
```
# ll /dev/disk/by-id
total 0
lrwxrwxrwx 1 root root 10 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684b -> ../../sdah
lrwxrwxrwx 1 root root 9 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684c -> ../../sdw
.
.
lrwxrwxrwx 1 root root 10 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684d -> ../../sdjk
lrwxrwxrwx 1 root root 10 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684e -> ../../sdaa
lrwxrwxrwx 1 root root 9 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684f -> ../../sdh
```
Also, you can find them using the Multipath command if you already have them configured with Multipath.
Multipath is mostly configured into the Oracle database server for better performance.
```
# multipath -ll
60a98000486e542d4f5a2f47694d684b dm-37 NETAPP,LUN C-Mode
size=512G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| |- 1:0:4:18 sdoe 128:416 active ready running
| |- 0:0:4:18 sdpq 131:256 active ready running
| |- 0:0:5:18 sdsr 135:496 active ready running
| `- 1:0:5:18 sdsq 135:480 active ready running
`-+- policy='round-robin 0' prio=10 status=enabled
|- 1:0:1:18 sdfw 131:32 active ready running
|- 1:0:0:18 sdci 69:96 active ready running
|- 0:0:1:18 sdbz 68:208 active ready running
|- 0:0:0:18 sds 65:32 active ready running
|- 1:0:3:18 sdmd 69:336 active ready running
|- 1:0:2:18 sdjj 8:464 active ready running
|- 0:0:3:34 sdjt 65:368 active ready running
`- 0:0:2:34 sdgi 131:224 active ready running
```
This procedure works on Red Hat 6.x, 7.x and 8.x (RHEL – Red Hat Enterprise Linux) based systems such as CentOS and Oracle Linux.
### Method-1: How to Scan New LUNs and SCSI Disks on Linux Using the “/sys” Class File
The sysfs filesystem is a pseudo-filesystem which provides an interface to kernel data structures.
The files under sysfs provide information about devices, kernel modules, filesystems, and other kernel components.
The sysfs filesystem is commonly mounted at “/sys”. Typically, it is mounted automatically by the system.
You can use the echo command to scan each scsi host device as shown below.
```
# echo "- - -" > /sys/class/scsi_host/host[n]/scan
```
When you run the above command that rescan everything, the three dash (“- – -“) refers the wildcard option. These values would be as follow.
```
# echo "c t l" > /sys/class/scsi_host/host[n]/scan
```
where
* **c –** Channel on the HBA
* **t –** SCSI target ID
* **l –** LUN ID
* **n –** HBA number
Run the below command to find all the host bus number on your system.
```
# ls /sys/class/scsi_host
host0 host1 host2
```
Once you get the host bus number, run the following command to discover new disks.
```
# echo "- - -" > /sys/class/scsi_host/host0/scan
# echo "- - -" > /sys/class/scsi_host/host1/scan
# echo "- - -" > /sys/class/scsi_host/host2/scan
```
Also, it can be scanned using “for loop” with a single command.
```
# for host in ls /sys/class/scsi_host/;do echo "- - -" >/sys/class/scsi_host/${host}/scan; done
```
You can check them using the **[ls command][2]** as mentioned at the beginning of the article.
```
# ls /dev/disk/by-id | grep -i "serial-hex of LUN"
```
### Method-2: How to Scan New LUNs and SCSI Disks on Linux Using the rescan-scsi-bus.sh Script
Make sure you have already installed the “sg3_utils” package to use this script. Otherwise, run the following command to install it.
For **RHEL/CentOS 6/7** systems, use the **[yum command][3]** to install sg3_utils.
```
# yum install -y sg3_utils
```
For **RHEL/CentOS 8** and Fedora systems, use the **[dnf command][4]** to install sg3_utils.
```
# dnf install -y sg3_utils
```
Now you can rescan the LUNs using the rescan-scsi-bus.sh script.
```
# ./rescan-scsi-bus.sh
```
--------------------------------------------------------------------------------
via: https://www.2daygeek.com/scan-detect-luns-scsi-disks-on-redhat-centos-oracle-linux/
作者：[Magesh Maruthamuthu][a]
选题：[lujun9972][b]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://www.2daygeek.com/author/magesh/
[b]: https://github.com/lujun9972
[1]: https://www.2daygeek.com/how-to-find-wwn-wwnn-wwpn-number-of-hba-card-in-linux/
[2]: https://www.2daygeek.com/linux-unix-ls-command-display-directory-contents/
[3]: https://www.2daygeek.com/linux-yum-command-examples-manage-packages-rhel-centos-systems/
[4]: https://www.2daygeek.com/linux-dnf-command-examples-manage-packages-fedora-centos-rhel-systems/

163
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View File

@ -0,0 +1,163 @@
[#]: collector: (lujun9972)
[#]: translator: (geekpi)
[#]: reviewer: ( )
[#]: publisher: ( )
[#]: url: ( )
[#]: subject: (How to Scan/Detect New LUNs and SCSI Disks on Linux)
[#]: via: (https://www.2daygeek.com/scan-detect-luns-scsi-disks-on-redhat-centos-oracle-linux/)
[#]: author: (Magesh Maruthamuthu https://www.2daygeek.com/author/magesh/)
如何在 Linux 上扫描/检测新的 LUN 和 SCSI 磁盘？
======
当 Linux 系统连接到 SAN（存储区域网络）后，你需要重新扫描 iSCSI 服务以发现新的 LUN。
要做到这一点，你必须向存储团队提供 Linux 主机的 WWN 号和所需的 LUN 大小。
下文将帮助你[**查找 Linux 主机的 WWN 号**][1]。
当存储团队将 LUN 与给定的 Linux 主机进行了映射，他们将为你提供新的 LUN 详细信息。
LUN 在存储术语中被称为 LUN 的串行十六进制。
你需要扫描 SCSI 主机来寻找存储团队分配的新 LUN。
这可以通过两种方式进行，扫描每个 scsi 主机设备或运行 “rescan-scsi-bus.sh” 脚本来检测新磁盘。
扫描后可以在 “/dev/disk/by-id” 目录下找到它们。
```
# ll /dev/disk/by-id
total 0
lrwxrwxrwx 1 root root 10 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684b -> ../../sdah
lrwxrwxrwx 1 root root 9 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684c -> ../../sdw
.
.
lrwxrwxrwx 1 root root 10 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684d -> ../../sdjk
lrwxrwxrwx 1 root root 10 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684e -> ../../sdaa
lrwxrwxrwx 1 root root 9 Jul 9 17:52 scsi-60a98000486e542d4f5a2f47694d684f -> ../../sdh
```
另外，如果你已经用 Multipath 配置了它们，那么可以用 Multipath 命令找到。
Multipath 主要是配置到 Oracle 数据库服务器中，以提高性能。
```
# multipath -ll
60a98000486e542d4f5a2f47694d684b dm-37 NETAPP,LUN C-Mode
size=512G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| |- 1:0:4:18 sdoe 128:416 active ready running
| |- 0:0:4:18 sdpq 131:256 active ready running
| |- 0:0:5:18 sdsr 135:496 active ready running
| `- 1:0:5:18 sdsq 135:480 active ready running
`-+- policy='round-robin 0' prio=10 status=enabled
|- 1:0:1:18 sdfw 131:32 active ready running
|- 1:0:0:18 sdci 69:96 active ready running
|- 0:0:1:18 sdbz 68:208 active ready running
|- 0:0:0:18 sds 65:32 active ready running
|- 1:0:3:18 sdmd 69:336 active ready running
|- 1:0:2:18 sdjj 8:464 active ready running
|- 0:0:3:34 sdjt 65:368 active ready running
`- 0:0:2:34 sdgi 131:224 active ready running
```
这个过程适用于基于 Red Hat 6.x、7.x 和 8.x（RHEL - Red Hat Enterprise Linux）的系统，如 CentOS 和 Oracle Linux。
### 方法 1：如何使用 “/sys” 类文件在 Linux 上扫描新的 LUN 和 SCSI 磁盘
sysfs 文件系统是一个伪文件系统，它为内核数据结构提供了一个接口。
sysfs 下的文件提供了关于设备、内核模块、文件系统和其他内核组件的信息。
sysfs 文件系统通常被挂载在 “/sys”。通常，它是由系统自动挂载的。
你可以使用 echo 命令来扫描每个 scsi 主机设备，如下所示：
```
# echo "- - -" > /sys/class/scsi_host/host[n]/scan
```
当你运行上面的重新扫描所有的命令时，三个破折号（“- – -“）指的是通配符选项。这些值如下：
```
# echo "c t l" > /sys/class/scsi_host/host[n]/scan
```
这里：
* **c –** HBA 上的通道
* **t –** SCSI 目标 ID
* **l –** LUN ID
* **n –** HBA 编号
运行下面的命令来查找系统中所有的主机总线编号：
```
# ls /sys/class/scsi_host
host0 host1 host2
```
得到主机总线编号后，运行以下命令来发现新的磁盘：
```
# echo "- - -" > /sys/class/scsi_host/host0/scan
# echo "- - -" > /sys/class/scsi_host/host1/scan
# echo "- - -" > /sys/class/scsi_host/host2/scan
```
另外，还可以用 ”for 循环“用一条命令进行扫描。
```
# for host in ls /sys/class/scsi_host/;do echo "- - -" >/sys/class/scsi_host/${host}/scan; done
```
你可以使用文章开头提到的 **[ls 命令][2]**来检查它们。
```
# ls /dev/disk/by-id | grep -i "serial-hex of LUN"
```
### 方法 2：如何使用 rescan-scsi-bus.sh 脚本在 Linux 上扫描新的 LUN 和 SCSI 磁盘
确保你已经安装了 “sg3_utils” 包来使用这个脚本。否则，运行以下命令来安装它。
对于 **RHEL/CentOS 6/7** 系统，使用 **[yum 命令][3]**安装 sg3_utils。
```
# yum install -y sg3_utils
```
对于 **RHEL/CentOS 8** 和 Fedora 系统，使用 **[dnf 命令][4]**安装 sg3_utils。
```
# dnf install -y sg3_utils
```
现在你可以使用 rescan-scsi-bus.sh 脚本重新扫描 LUN。
```
# ./rescan-scsi-bus.sh
```
--------------------------------------------------------------------------------
via: https://www.2daygeek.com/scan-detect-luns-scsi-disks-on-redhat-centos-oracle-linux/
作者：[Magesh Maruthamuthu][a]
选题：[lujun9972][b]
译者：[geekpi](https://github.com/geekpi)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]: https://www.2daygeek.com/author/magesh/
[b]: https://github.com/lujun9972
[1]: https://www.2daygeek.com/how-to-find-wwn-wwnn-wwpn-number-of-hba-card-in-linux/
[2]: https://www.2daygeek.com/linux-unix-ls-command-display-directory-contents/
[3]: https://www.2daygeek.com/linux-yum-command-examples-manage-packages-rhel-centos-systems/
[4]: https://www.2daygeek.com/linux-dnf-command-examples-manage-packages-fedora-centos-rhel-systems/