rp8420机器，安装了4块硬盘，vg00是用两个硬盘做，另外两个硬盘没有做vg，其中没有做vg硬盘经常离线，具体如下：
#ioscan -fnNC disk | pg
Class I H/W Path Driver S/W State H/W Type Description
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disk 5 64000/0xfa00/0x5 esdisk CLAIMED DEVICE _NEC DVD+RW ND-2100AD
/dev/disk/disk5 /dev/rdisk/disk5
disk 6 64000/0xfa00/0x6 esdisk CLAIMED DEVICE HP 73.4GST373454LC
/dev/disk/disk6 /dev/rdisk/disk6
disk 7 64000/0xfa00/0x7 esdisk NO_HW DEVICE HP 73.4GST373454LC
/dev/disk/disk7 /dev/rdisk/disk7
disk 8 64000/0xfa00/0x8 esdisk CLAIMED DEVICE HP 73.4GMAU3073NC
/dev/disk/disk8 /dev/rdisk/disk8
disk 9 64000/0xfa00/0x9 esdisk CLAIMED DEVICE HP 73.4GMAU3073NC
/dev/disk/disk9 /dev/rdisk/disk9
（1）更换SCSI背板和SCSI连接线，开始正常，过了几个小时，还是以上现象。
（2）把disk7和disk9硬盘对换了一下，然后用ioscan -fnNC disk | pg ，看disk7和disk9都是NO_HW。
请问一下以下现象，是什么问题？
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