Centos添加硬盘时(SCSI -->系统上电运行过程只能添加SCSI硬盘)，一般刚添加上系统不会识别到，我们重启后就可以识别出来了，是否有可以不重启系统即可识别出我们新添加的硬盘，其实可以的：
添加新的磁盘，查看/dev/ 此时并没有出现新的磁盘/dev/sdb:
[root@MiWiFi-R3-srv ~]# ls /dev/s
scd0 sda1 sda3 sg1 snapshot stderr stdout
sda sda2 sg0 shm/ sr0 stdin systty
[root@MiWiFi-R3-srv ~]# fdisk -l
Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000a47d7
Device Boot Start End Blocks Id System
/dev/sda1 * 1 52 409600 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 52 574 4194304 82 Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3 574 5222 37338112 83 Linux
确定主机总线号：
[root@MiWiFi-R3-srv ~]# ls /sys/class/scsi_host/
host0 host1 host2
[root@MiWiFi-R3-srv ~]#
重新扫描SCSI总线来添加设备：
[root@MiWiFi-R3-srv ~]# echo "- - -" > /sys/class/scsi_host/host0/scan
[root@MiWiFi-R3-srv ~]# echo "- - -" > /sys/class/scsi_host/host1/scan
[root@MiWiFi-R3-srv ~]# echo "- - -" > /sys/class/scsi_host/host2/scan
[root@MiWiFi-R3-srv ~]# fdisk -l
Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000a47d7
Device Boot Start End Blocks Id System
/dev/sda1 * 1 52 409600 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 52 574 4194304 82 Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3 574 5222 37338112 83 Linux
Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
[root@MiWiFi-R3-srv ~]# ls /dev/sd
sda sda1 sda2 sda3 sdb