linux添加新LUN，无需重启

在给存储增加新的Lun时，在linux下一般是：

A.重启操作系统
B.重启HBA卡驱动

1. kudzu
添加完新硬盘后，运行命令kudzu重新扫描新的硬件设备，类似aix的cfgmgr

eg：
[root@skatedb]#  kudzu -p | more
-
class: OTHER
bus: PCI
detached: 0
driver: shpchp
desc: "VMware PCI Express Root Port"
vendorId: 15ad
deviceId: 07a0
subVendorId: 0000
subDeviceId: 0000
pciType: 1
pcidom:    0
pcibus:  0
pcidev: 18
pcifn:  7
-
class: OTHER
bus: PCI
detached: 0
driver: shpchp
desc: "VMware PCI Express Root Port"
vendorId: 15ad
deviceId: 07a0

官方解释：
DESCRIPTION
       kudzu  detects  and configures new and/or changed hardware on a system.
    When started, kudzu detects the current hardware, and checks it against
    a database stored in /etc/sysconfig/hwconf, if  one  exists.  It
       then determines if any hardware has been added or removed from the system.
    If so, it gives the users the opportunity to configure any added hardware,
    and unconfigure any removed hardware. It then  updates  the database 
    in /etc/sysconfig/hwconf.

2.直接修改文件权限，让系统重新扫描新的硬件设备

在RHEL4，5之下，在/sys/class/scsi_host/hostX文件系统中找到对应的卡的目录，
会存在一个文件叫做scan。该文件的权限只有write，没有read。
只需要执行echo "- - -" > scan即可扫描对应的新LUN

查看机器有几块HBA卡
[root@skatedb] ls /sys/class/fc_host/
host1

[root@skatedb~]# ls /sys/class/scsi_host/host0/
cmd_per_lun  hba_bios_version     host_busy    model       scan           state      unchecked_isa_dma
device       hba_kernel_version   max_channel  proc_name   serial_number  subsystem  unique_id
flags        hba_monitor_version  max_id       reset_host  sg_tablesize   uevent     vendor

[root@skatedb~]# ls -l /sys/class/scsi_host/host0/scan
--w------- 1 root root 4096 Dec 12 18:51 /sys/class/scsi_host/host0/scan

修改文件“scan”权限，
[root@skatedb~]# echo "- - -" > /sys/class/scsi_host/host0/scan

查看
[root@skatedb~]# fdisk -l

记录一篇英文参考：

Dynamically adding storage for use with multipath I/O

This document (3000817) is provided subject to the disclaimer at the end of this document.
Environment
SUSE Linux Enterprise Server 10
SUSE Linux Enterprise Server 9
Novell Open Enterprise Server (Linux based)

SAN suited for multiple paths to storage

The Linux installation has already been configured to use Device-Mapper Multipath I/O (DM-MPIO) per the article "How to setup / use multipathing on SLES".

The Linux driver for the host base adapters (HBAs) on the system supports rescanning the HBA to detect the addition or deletion of storage areas ("SAN disks"). For example, a QLogic or Emulex HBA is being used.

The system has been booted with kernel parameters for SCSI device scanning that are appropriate for the SCSI device numbering plan being followed in the SAN and for the SCSI levels reported by the HBAs as discussed in TID 3955167 - Troubleshooting SCSI (LUN) scanning issues.
Situation
Purpose
Adding SAN storage to the Linux system and setting up multiple I/O paths to it without needing to reboot the system. 
Resolution
Follow these steps to allocate new storage on the SAN, make it visible to the Linux system and use it to create new filesystems or to expand existing filesystems residing on logical volumes:
Allocate the storage on the SAN and update its access control settings to allow the Linux system access to the new storage. How this is done in detail is highly dependent on the components of the SAN and its architecture; refer to the SAN vendor‘s documentation for details.

On the Linux system, instruct the HBA driver to rescan the SAN to discover the new storage area ("LUN"). The exact commands depend on the kernel version and driver.

With SLES10, a LIP (Loop Initialization Procedure) can be issued to both Qlogic and Emulex drivers through sysfs:
echo 1 > /sys/class/fc_host/host/issue_lip

With SLES9 and OES/Linux, the Qlogic and Emulex drivers require different commands for rescanning. For example, for a QLogic 2300 HBA, the command is
echo scsi-qlascan > /proc/scsi/qla2xxx/
whereas for an Emulex HBA, it is
echo 1 > /sys/class/scsi_host/host/issue_lip

If the HBA driver supports it, check that the new disk is seen by the HBA driver correctly (at this point, the newly added LUN will not yet be known to the higher layers of the Linux kernel‘s SCSI subsystem and will not yet be usable).

With SLES10, after the LIP, a directory for the new disk should have been created under /sys/class/fc_remote_ports/ containing information such as port ID and port name.

With SLES9 or OES/Linux, for a QLogic 2300 HBA, run
less /proc/scsi/qla2xxx/
and check the "SCSI LUN information" section. The entries for the newly added disks are indicated by a "*" after the flags.
Unfortunately, there is no equivalent for Emulex cards.

Make the new device known to the middle layer of the Linux kernel‘s SCSI subsystem. This can be done in two ways.
Through the
rescan-scsi-bus.sh
command which rescans the SCSI subsystem for changes. Depending on the SCSI device numbering plan in use, arguments may need to be used to enlarge the scope of the search or to control it more carefully, e.g through
rescan-scsi-bus.sh -l -w -c
which will search LUNs other than 0, scan for more device IDs and for more channels, or through
rescan-scsi-bus.sh --hosts="hostlist" --channels="channellist" --ids="idlist" --luns="lunlist"
Alternatively, one can
echo "scsi add-single-device 0 1 2 3" > /proc/scsi/scsi
to add the storage with host ID 0, channel ID 1, target ID 2, LUN ID 3, or, with kernel 2.6.5-7.257 or newer,
echo "- - -" > /sys/class/scsi_host/host/scan
to rescan all targets on a host.

Run
multipath
to have the new devices be picked up for DM-MPIO.
Examine /dev/disk/by-id to identify the persistent device names for the new storage area(s) and use the persistent device names for further operations (including filesystem creation and addition to /etc/fstab).
If LVM is to be used for the new storage area(s), configure LVM at this point, either through YaST or using the LVM command line tools, starting with pvcreate.

linux添加新LUN，无需重启