VMware Workstation 为CentOS虚拟机不重启添加SCSI硬盘
大纲
1、通过VMware Workstation为虚拟机添加硬盘
2、强制Linux扫描SCSI设备
It is possible to add or remove a SCSI device explicitly, or to rescan an entire SCSI bus without rebooting a running Linux VM guest.
All instructions are tested on RHEL, Fedora, CentOS and Ubuntu Linux guest / hosts operating systems.
一般情况下，我们可以通过VMware给虚拟机添加硬盘，但是需要重启虚拟机才可以识别新增的磁盘。我们能不能在线新增磁盘，而不重新启动呢？ 答案是肯定的。
1、通过VMware Workstation为虚拟机添加硬盘
1、在线为CentOS添加磁盘，点击VM > Settings
在弹出的Virtual Machine Settings窗口中，选择下方的 "Add" 按钮。
然后进入"Add Hardware Wizard"添加硬件向导,选择 "Hard Disk", 然后 "Next"
接下来选择“Disk Type”,我们选择 SCSI（Small Computer System Interface）,即小型计算机系统接口 ， 不能选择IDE，VMware也非常友好的提示"Cannot be added while the VM is powerd on"。为什么呢？ 因为IDE接口的硬盘是不支持热插拔的设备，所以我们必须选择SCSI或者SATA类型的接口，支持热插拔的类型才行。
下一步，我们直接选择"Create a new virtual disk"，创建一个新的虚拟磁盘，如果你想添加已经存在的虚拟磁盘，请选择第2项，这里不建议选择第3项"Use a physical disk"
选择磁盘大小，根据自己的需要合理指定大小即可。
Allocate all disk space now. 选择它，那么会立刻在我们物理磁盘上申请并分配我们指定的大小空间，可以提高虚拟机的性能，但是会占用更多的空间。相反，如果不勾选它，默认情况下，消耗的空间根据实际虚拟机中占用的磁盘空间大小动态分配。
Store virtual disk as a single file. 把虚拟磁盘存储为单个文件，如果宿主机文件系统是NTFS，那么建议选择它。
Split virtual disk into multiple files. 把虚拟磁盘切割为多块存储在多个文件中，这样可以更容易移动到其他计算机上，但是可能降低性能。其实我认为最主要的原因是某些文件系统,如FAT的单个文件最大限制为4G，所以切分为多个文件进行存储，可以避免单个文件过大而无法存储的问题。
然后点击"Finish", 即添加成功。
看，我们现在有两块磁盘了哦。
2、强制Linux扫描SCSI设备
通常，磁盘添加完成后，需要重启一下计算机，内核会自动检测到这个新的设备。我们可以使用
# ls /dev/sd*
来查看，一般是以/dev/sd[a-z]命名的设备文件。
但是，在生产环境中，是不允许我们随意重启服务器的，我们会尽可能的选择不重启系统的方式来解决，现在我们就来探讨一种不重启而让内核检测到SCSI磁盘的方法。
Replace host# with actual value such as host0. You can find scsi_host value using the following command:
# ls /sys/class/scsi_host
Output: host0
Now type the following to send a rescan request:
# echo "- - -" > /sys/class/scsi_host/host0/scan
# fdisk -l
# tail -f /var/log/message
1、以root用户执行下面的命令，强制内核再次检测PCI设备：
[root@localhost ~]# ls /dev/sd* /dev/sda /dev/sda1 /dev/sda2 /dev/sda3 [root@localhost ~]# echo '- - -' > /sys/class/scsi_host/host0/scan [root@localhost ~]# ls /dev/sd* /dev/sda /dev/sda1 /dev/sda2 /dev/sda3 /dev/sdb [root@localhost ~]# fdisk -l [root@localhost ~]# tail -f /var/log/message
最关键的是这一行命令：
注意：三个"- - -"号之间有空格。
执行完这条命令后，再执行 ls /dev/sd* 命令，就能发现新添加的磁盘 /dev/sdb，查看系统日志/var/log/messages，发现对SCSI设备进行了一次重新扫描。
可以看到有如图的相关信息。
OK，至此我们已经顺利新增了一块磁盘，那么接下来可以进行fdisk分区，mkfs格式化等操作了。
下面有更详尽的描述：
http://hi.baidu.com/doughtymild/item/ad2096fd80ff9ecf521c2609
Step # 2: Rescan the SCSI Bus to Add a SCSI Device Without rebooting the VMA rescan can be issued by typing the following command: # echo "- - -" > /sys/class/scsi_host/host#/scan # fdisk -l # tail -f /var/log/message
Sample outputs:
Replace host# with actual value such as host0. You can find scsi_host value using the following command: # ls /sys/class/scsi_host Output: host0 # host0 Now type the following to send a rescan request: # echo "- - -" > /sys/class/scsi_host/host0/scan # host0 # fdisk -l # tail -f /var/log/message
Sample Outputs:
Jul 18 16:29:39 localhost kernel: Vendor: VMware, Model: VMware Virtual S Rev: 1.0 Jul 18 16:29:39 localhost kernel: Type: Direct-Access ANSI SCSI revision: 02 Jul 18 16:29:39 localhost kernel: target0:0:1: Beginning Domain Validation Jul 18 16:29:39 localhost kernel: target0:0:1: Domain Validation skipping write tests Jul 18 16:29:39 localhost kernel: target0:0:1: Ending Domain Validation Jul 18 16:29:39 localhost kernel: target0:0:1: FAST-40 WIDE SCSI 80.0 MB/s ST (25 ns, offset 127) Jul 18 16:29:39 localhost kernel: SCSI device sdb: 2097152 512-byte hdwr sectors (1074 MB) Jul 18 16:29:39 localhost kernel: sdb: Write Protect is off Jul 18 16:29:39 localhost kernel: sdb: cache data unavailable Jul 18 16:29:39 localhost kernel: sdb: assuming drive cache: write through Jul 18 16:29:39 localhost kernel: SCSI device sdb: 2097152 512-byte hdwr sectors (1074 MB) Jul 18 16:29:39 localhost kernel: sdb: Write Protect is off Jul 18 16:29:39 localhost kernel: sdb: cache data unavailable Jul 18 16:29:39 localhost kernel: sdb: assuming drive cache: write through Jul 18 16:29:39 localhost kernel: sdb: unknown partition table Jul 18 16:29:39 localhost kernel: sd 0:0:1:0: Attached scsi disk sdb Jul 18 16:29:39 localhost kernel: sd 0:0:1:0: Attached scsi generic sg1 type 0 Jul 18 16:29:39 localhost kernel: Vendor: VMware, Model: VMware Virtual S Rev: 1.0 Jul 18 16:29:39 localhost kernel: Type: Direct-Access ANSI SCSI revision: 02 Jul 18 16:29:39 localhost kernel: target0:0:2: Beginning Domain Validation Jul 18 16:29:39 localhost kernel: target0:0:2: Domain Validation skipping write tests Jul 18 16:29:39 localhost kernel: target0:0:2: Ending Domain Validation Jul 18 16:29:39 localhost kernel: target0:0:2: FAST-40 WIDE SCSI 80.0 MB/s ST (25 ns, offset 127) Jul 18 16:29:39 localhost kernel: SCSI device sdc: 2097152 512-byte hdwr sectors (1074 MB) Jul 18 16:29:39 localhost kernel: sdc: Write Protect is off Jul 18 16:29:39 localhost kernel: sdc: cache data unavailable Jul 18 16:29:39 localhost kernel: sdc: assuming drive cache: write through Jul 18 16:29:39 localhost kernel: SCSI device sdc: 2097152 512-byte hdwr sectors (1074 MB) Jul 18 16:29:39 localhost kernel: sdc: Write Protect is off Jul 18 16:29:39 localhost kernel: sdc: cache data unavailable Jul 18 16:29:39 localhost kernel: sdc: assuming drive cache: write through Jul 18 16:29:39 localhost kernel: sdc: unknown partition table Jul 18 16:29:39 localhost kernel: sd 0:0:2:0: Attached scsi disk sdc Jul 18 16:29:39 localhost kernel: sd 0:0:2:0: Attached scsi generic sg2 type 0
How Do I Delete a Single Device Called /dev/sdc?
In addition to re-scanning the entire bus, a specific device can be added or existing device deleted using the following command:
### echo 1 > /sys/block/devName/device/delete # devName # echo 1 > /sys/block/sdc/device/delete # sdc
How Do I Add a Single Device Called /dev/sdc?
To add a single device explicitly, use the following syntax:
# echo "scsi add-single-device <H> <B> <T> <L>" > /proc/scsi/scsi
Where,
<H> : Host
<B> : Bus (Channel)
<T> : Target (Id)
<L> : LUN numbers
For e.g. add /dev/sdc with host # 0, bus # 0, target # 2, and LUN # 0, enter:
# echo "scsi add-single-device 0 0 2 0">/proc/scsi/scsi # fdisk -l # cat /proc/scsi/scsi
Sample Outputs:
Attached devices: Host: scsi0 Channel: 00 Id: 00 Lun: 00 Vendor: VMware, Model: VMware Virtual S Rev: 1.0 Type: Direct-Access ANSI SCSI revision: 02 Host: scsi0 Channel: 00 Id: 01 Lun: 00 Vendor: VMware, Model: VMware Virtual S Rev: 1.0 Type: Direct-Access ANSI SCSI revision: 02 Host: scsi0 Channel: 00 Id: 02 Lun: 00 Vendor: VMware, Model: VMware Virtual S Rev: 1.0 Type: Direct-Access ANSI SCSI revision: 02Step #3: Format a New Disk
Now, you can create partition using fdisk and format it using mkfs.ext3command:
# fdisk /dev/sdc
# mkfs.ext3 /dev/sdc3
Step #4: Create a Mount Point And Update /etc/fstab
# mkdir /disk3
Open /etc/fstab file, enter:
# vi /etc/fstab
Append as follows:
/dev/sdc3 /disk3 ext3 defaults 1 2
Save and close the file.
Optional Task: Label the partition
You can label the partition using e2label. For example, if you want to label the new partition /backupDisk, enter
# e2label /dev/sdc1 /backupDisk
Conclusion
The VMware guest now has an additional virtualized storage device. The procedure works for all physical block devices, this includes CD-ROM, DVD and floppy devices. Next, time I will write about adding an additional virtualized storage device using XEN software.