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。
在ESXi或者vCenter中添加一块新的20G硬盘：
注：以上图片上传到红联Linux系统教程频道中。
显示当前磁盘分区：
[root@centos7 ~]# fdisk -l
Disk/dev/sda:32.2 GB,32212254720 bytes,62914560 sectors
Units= sectors of 1*512=512 bytes
Sector size (logical/physical):512 bytes /512 bytes
I/O size (minimum/optimal):512 bytes /512 bytes
Disk label type: dos
Disk identifier:0x0006b96a
DeviceBootStartEndBlocksIdSystem
/dev/sda1 *2048102604751200083Linux
/dev/sda2 102604862914559309442568eLinux LVM
Disk/dev/mapper/centos-swap:2147 MB,2147483648 bytes,4194304 sectors
Units= sectors of 1*512=512 bytes
Sector size (logical/physical):512 bytes /512 bytes
I/O size (minimum/optimal):512 bytes /512 bytes
Disk/dev/mapper/centos-root:29.5 GB,29536288768 bytes,57688064 sectors
Units= sectors of 1*512=512 bytes
Sector size (logical/physical):512 bytes /512 bytes
I/O size (minimum/optimal):512 bytes /512 bytes
确定主机总线号
[root@centos7 ~]# ls /sys/class/scsi_host/
host0 host1 host2
重新扫描SCSI总线来添加设备
[root@centos7 ~]# echo "- - -">/sys/class/scsi_host/host0/scan
[root@centos7 ~]# echo "- - -">/sys/class/scsi_host/host1/scan
[root@centos7 ~]# echo "- - -">/sys/class/scsi_host/host2/scan
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：
[root@centos7 ~]# fdisk -l
Disk/dev/sda:32.2 GB,32212254720 bytes,62914560 sectors
Units= sectors of 1*512=512 bytes
Sector size (logical/physical):512 bytes /512 bytes
I/O size (minimum/optimal):512 bytes /512 bytes
Disk label type: dos
Disk identifier:0x0006b96a
DeviceBootStartEndBlocksIdSystem
/dev/sda1 *2048102604751200083Linux
/dev/sda2 102604862914559309442568eLinux LVM
Disk/dev/mapper/centos-swap:2147 MB,2147483648 bytes,4194304 sectors
Units= sectors of 1*512=512 bytes
Sector size (logical/physical):512 bytes /512 bytes
I/O size (minimum/optimal):512 bytes /512 bytes
Disk/dev/mapper/centos-root:29.5 GB,29536288768 bytes,57688064 sectors
Units= sectors of 1*512=512 bytes
Sector size (logical/physical):512 bytes /512 bytes
I/O size (minimum/optimal):512 bytes /512 bytes
Disk/dev/sdb:21.5 GB,21474836480 bytes,41943040 sectors
Units= sectors of 1*512=512 bytes
Sector size (logical/physical):512 bytes /512 bytes
I/O size (minimum/optimal):512 bytes /512 bytes