Managing Multipath I/O for Devices
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The following information is displayed for each group:
Scheduling policy used to balance I/O within the group, such as round-robin
Whether the group is active, disabled, or enabled
Whether the group is the first (highest priority) one
Paths contained within the group
The following information is displayed for each path:
The physical address as
host:bus:target:lun
, such as 1:0:1:2
Device node name, such as
sda
Major:minor numbers
Status of the device
5.14 Scanning for New Devices without
Rebooting
If your system has already been configured for multipathing and you later need to add more storage
to the SAN, use the following procedure to scan the devices and make them available to
multipathing without rebooting the system.
1
On the storage subsystem, use the vendor’s tools to allocate the devices and update its access
control settings to allow the Linux system access to the new storage. Refer to the vendor’s
documentation for details.
2
On the Linux system, scan the SAN at a low level to discover the new devices. At a terminal
console prompt, enter
echo 1 > /sys/class/fc_host/host<number>/issue_lip
For example, to probe the HBA on host1, enter
echo 1 > /sys/class/fc_host/host1/issue_lip
At this point, the newly added device is not known to the higher layers of the Linux kernel's
SCSI subsystem and is not yet usable.
3
Scan all targets for a host to make its new device known to the middle layer of the Linux
kernel's SCSI subsystem. At a terminal console prompt, enter
echo "- - -" > /sys/class/scsi_host/host<number>/scan
For example, to probe the HBA on host1, enter
echo "- - -" > /sys/class/scsi_host/host1/scan
4
Check for scanning progress in the system log (the
/var/log/messages
file). At a
terminal console prompt, enter
tail -30 /var/log/messages
This command displays the last 30 lines of the log. For example:
# tail -30 /var/log/messages
. . .
Feb 14 01:03 kernel: SCSI device sde: 81920000
Feb 14 01:03 kernel: SCSI device sdf: 81920000
Feb 14 01:03 multipathd: sde: path checker registered
Feb 14 01:03 multipathd: sdf: path checker registered
Summary of Contents for LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE 7-2007
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