Linux在线扫描热添加的SCSI/iSCSI设备

SCSI接口具有应用范围广、多任务、带宽大、CPU占用率低，以及热插拔等优点，在服务器中广泛的应用。

当然在虚拟化平台支持下，也能模拟出SCSI设备，方便在虚拟机上热添加SCSI设备（一般是硬盘）

但是在热添加SCSI设备之后，需要手动rescan SCSI设备。

比较常见的做法是输入如下命令

echo "- - -" > /sys/class/scsi_host/host*/scan

CentOS/RHEL5.9开始（SUSE11/12也有这个工具）提供一个工具包sg3_utils同样可以方便的实现rescan操作

# yum install sg3_utils
# /usr/bin/rescan-scsi-bus.sh
即可rescan SCSI设备

以下是rescan-scsi-bus.sh的说明

# /usr/bin/rescan-scsi-bus.sh --help
Usage: rescan-scsi-bus.sh [options] [host [host ...]]
Options:
 -a      scan all targets, not just currently existing [default: disabled]
 -d      enable debug                       [default: 0]
 -l      activates scanning for LUNs 0--7   [default: 0]
 -L NUM  activates scanning for LUNs 0--NUM [default: 0]
 -w      scan for target device IDs 0--15   [default: 0--7]
 -c      enables scanning of channels 0 1   [default: 0 / all detected ones]
 -m      update multipath devices           [default: disabled]
 -r      enables removing of devices        [default: disabled]
 -f      flush failed multipath devices     [default: disabled]
 -i      issue a FibreChannel LIP reset     [default: disabled]
 -u      look for existing disks that have been remapped
 -s      look for resized disks and reload associated multipath devices, if applicable
--alltargets:    same as -a
--remove:        same as -r
--flush:         same as -f
--issue-lip:     same as -i
--wide:          same as -w
--multipath:     same as -m
--forceremove:   Remove stale devices (DANGEROUS)
--forcerescan:   Remove and readd existing devices (DANGEROUS)
--nooptscan:     don't stop looking for LUNs if 0 is not found
--color:         use coloured prefixes OLD/NEW/DEL
--hosts=LIST:    Scan only host(s) in LIST
--channels=LIST: Scan only channel(s) in LIST
--ids=LIST:      Scan only target ID(s) in LIST
--luns=LIST:     Scan only lun(s) in LIST
--sync/nosync:   Issue a sync / no sync [default: sync if remove]
--attachpq3:     Tell kernel to attach sg to LUN 0 that reports PQ=3
--reportlun2:    Tell kernel to try REPORT_LUN even on SCSI2 devices
--largelun:      Tell kernel to support LUNs > 7 even on SCSI2 devs
--sparselun:     Tell kernel to support sparse LUN numbering
--update:        same as -u
--resize:        same as -s
 Host numbers may thus be specified either directly on cmd line (deprecated) or
 or with the --hosts=LIST parameter (recommended).
LIST: A[-B][,C[-D]]... is a comma separated list of single values and ranges
 (No spaces allowed.)

本文参考链接如下

How do I rescan an HP Smart Array for new devices without rebooting?

How to rescan the SCSI bus to add or remove a SCSI device without rebooting the computer

ADDING/REMOVING A LOGICAL UNIT THROUGH RESCAN-SCSI-BUS.SH

HOWTO: Add, Resize and Remove LUN without restarting SLES or OES Linux