不重启Linux主机来识别新加的硬盘

生产系统在没有计划重启的情况下，不是随时都可以重启，Linux主机在扩容添加lun存储或者磁盘时，通常需要进行重启系统才能识别新添加的lun，本测试通过重置存储缓冲值的方式来发现新添加的存储，达到不重启系统也能发现新添加的磁盘存储的目的1.当前操作系统环境实验环境#cat /etc/redhat-release Red Hat Enterprise Linux Server release 6.7 (Santiago)#uname  -arLinux ASMdb01 2.6.32-573.el6.x86_64 #1 SMP Wed Jul 1 18:23:37 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux#dmidecode | grep -i vmware        Manufacturer: VMware, Inc.        Product Name: VMware Virtual Platform        Serial Number: VMware-56 4d 8a c5 73 b5 c7 b6-22 cc 7c 33 8e 12 c8 38        Description: VMware SVGA II2.添加磁盘新添加5块磁盘，一块50GB,4块30GB后利用fdisk -l 查看当前磁盘状态,新添加磁盘并没有被识别出来#fdisk -l Disk /dev/sda: 26.8 GB, 26843545600 bytes   Device Boot      Start         End      Blocks   Id  System/dev/sda1   *           1          26      204800   83  LinuxPartition 1 does not end on cylinder boundary./dev/sda2              26        3264    26008576   8e  Linux LVMDisk /dev/mapper/VolGroup-LogVol01: 24.5 GB, 24482152448 bytesDisk identifier: 0x00000000Disk /dev/mapper/VolGroup-LogVol00: 2147 MB, 2147483648 bytesDisk identifier: 0x00000000（注:此处省略fdisk -l 部分详细信息）3.进入/sys/class/scsi_host目录，在/sys/class/scsi_host下找到符合指向本机iscsi设备主机符号链接表# ls -al  /sys/class/scsi_hosttotal 0drwxr-xr-x.  2 root root 0 Nov 12 15:31 .drwxr-xr-x. 45 root root 0 Nov 12 15:31 ..lrwxrwxrwx.  1 root root 0 Nov 12 15:31 host0 -> ../../devices/pci0000:00/0000:00:07.1/host0/scsi_host/host0lrwxrwxrwx.  1 root root 0 Nov 12 15:31 host1 -> ../../devices/pci0000:00/0000:00:07.1/host1/scsi_host/host1lrwxrwxrwx.  1 root root 0 Nov 12 15:31 host2 -> ../../devices/pci0000:00/0000:00:10.0/host2/scsi_host/host2本目录下有三个host，分别是host0,host1,host2，在这三个host中，需要确定本机是host0，host1还是host2，在确定host号后，通过重置相应的host存储缓存值就可以发现新添加的硬件了4.确定需要重置的host号利用grep命令,通过过滤smpspi模块的输出值来确定哪个host链接需要重置,分别查看host0,host1,host2，有mptspi模块值输出的，就是本机需要进行重置的host# grep mpt /sys/class/scsi_host/host0/proc_name# grep mpt /sys/class/scsi_host/host1/proc_namehost2的输出值是mptspi,最终确定host2是需要重置存储缓冲值的host# grep mpt /sys/class/scsi_host/host2/proc_namemptspi5.确定host后，重置host2的存储缓存值注:echo "- - -" > /sys/class/scsi_host/host2/scan  “ - - - ”定义了存储在host2中扫描内的三个值，本别是，通道号、SCSI目标ID、LUN值,该命令用通配符替换值，以便它可以检测附加到Linux主机上的新变化。# echo "- - -" > /sys/class/scsi_host/host2/scan6.再次查看fdisk，发现系统已经发现新添加的磁盘了，实验完成。# fdisk -l Disk /dev/sda: 26.8 GB, 26843545600 bytes255 heads, 63 sectors/track, 3263 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk identifier: 0x00066506   Device Boot      Start         End      Blocks   Id  System/dev/sda1   *           1          26      204800   83  LinuxPartition 1 does not end on cylinder boundary./dev/sda2              26        3264    26008576   8e  Linux LVMDisk /dev/mapper/VolGroup-LogVol01: 24.5 GB, 24482152448 bytes Disk /dev/mapper/VolGroup-LogVol00: 2147 MB, 2147483648 bytes Disk /dev/sdb: 53.7 GB, 53687091200 bytes Disk /dev/sdc: 32.2 GB, 32212254720 bytes Disk /dev/sdd: 32.2 GB, 32212254720 bytes Disk /dev/sde: 32.2 GB, 32212254720 bytes Disk /dev/sdf: 32.2 GB, 32212254720 bytes255 heads, 63 sectors/track, 3916 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk identifier: 0x00000000 注:此处省略fdisk -l 详细输出信息