通常在你在虚拟机中添加一块新硬盘时，你可能会看到新硬盘没有自动加载。这是因为连接到硬盘的SCSI总线需要重新扫描来使得新硬盘可见。这里有一个简单的命令来重新扫描SCSI总线和SCSI设备。下面这几步在CentOS 7 和RHEL 7 中测试过。

1. 在ESXi或者vCenter中添加一块新的20G硬盘：

   

2. 显示当前磁盘分区：

   1. [root@centos7 ~]# fdisk -l

   ---

   1. Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 sectors
   2. Units = sectors of 1 * 512 = 512 bytes
   3. Sector size (logical/physical): 512 bytes / 512 bytes
   4. I/O size (minimum/optimal): 512 bytes / 512 bytes
   5. Disk label type: dos
   6. Disk identifier: 0x0006b96a
   8. Device Boot Start End Blocks Id System
   9. /dev/sda1 * 2048 1026047 512000 83 Linux
   10. /dev/sda2 1026048 62914559 30944256 8e Linux LVM
   12. Disk /dev/mapper/centos-swap: 2147 MB, 2147483648 bytes, 4194304 sectors
   13. Units = sectors of 1 * 512 = 512 bytes
   14. Sector size (logical/physical): 512 bytes / 512 bytes
   15. I/O size (minimum/optimal): 512 bytes / 512 bytes
   17. Disk /dev/mapper/centos-root: 29.5 GB, 29536288768 bytes, 57688064 sectors
   18. Units = sectors of 1 * 512 = 512 bytes
   19. Sector size (logical/physical): 512 bytes / 512 bytes
   20. I/O size (minimum/optimal): 512 bytes / 512 bytes

3. 确定主机总线号

   1. [root@centos7 ~]# ls /sys/class/scsi_host/
   2. host0 host1 host2

4. 重新扫描SCSI总线来添加设备

   1. [root@centos7 ~]# echo "- - -" > /sys/class/scsi_host/host0/scan
   2. [root@centos7 ~]# echo "- - -" > /sys/class/scsi_host/host1/scan
   3. [root@centos7 ~]# echo "- - -" > /sys/class/scsi_host/host2/scan

5. 验证磁盘和分区并确保20GB硬盘已经添加了。在本例中，出现了下面这行 “Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors” 并且可以确认没有重启服务器就添加了新盘：

   1. [root@centos7 ~]# fdisk -l
   3. Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 sectors
   4. Units = sectors of 1 * 512 = 512 bytes
   5. Sector size (logical/physical): 512 bytes / 512 bytes
   6. I/O size (minimum/optimal): 512 bytes / 512 bytes
   7. Disk label type: dos
   8. Disk identifier: 0x0006b96a
   10. Device Boot Start End Blocks Id System
   11. /dev/sda1 * 2048 1026047 512000 83 Linux
   12. /dev/sda2 1026048 62914559 30944256 8e Linux LVM
   14. Disk /dev/mapper/centos-swap: 2147 MB, 2147483648 bytes, 4194304 sectors
   15. Units = sectors of 1 * 512 = 512 bytes
   16. Sector size (logical/physical): 512 bytes / 512 bytes
   17. I/O size (minimum/optimal): 512 bytes / 512 bytes
   19. Disk /dev/mapper/centos-root: 29.5 GB, 29536288768 bytes, 57688064 sectors
   20. Units = sectors of 1 * 512 = 512 bytes
   21. Sector size (logical/physical): 512 bytes / 512 bytes
   22. I/O size (minimum/optimal): 512 bytes / 512 bytes
   24. Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
   25. Units = sectors of 1 * 512 = 512 bytes
   26. Sector size (logical/physical): 512 bytes / 512 bytes
   27. I/O size (minimum/optimal): 512 bytes / 512 bytes