Scanning FC-LUN’s in Redhat Linux
1.First, find out how many disks are visible in “fdisk -l” .# fdisk -l 2>/dev/null | egrep '^Disk' | egrep -v 'dm-' | wc -l2.Find out how many host bus adapter configured in the Linux box.you can use “systool -fc_host -v” to verify available FC in the system.
# ls /sys/class/fc_host host0 host1In this case,you need to scan host0 & host1 HBA.
3.If the system virtual memory is too low ,then do not proceed further.If you have enough free virtual memory,then you can proceed with below command to scan new LUNS.
# echo "1" > /sys/class/fc_host/host0/issue_lip # echo "- - -" > /sys/class/scsi_host/host0/scan # echo "1" > /sys/class/fc_host/host1/issue_lip # echo "- - -" > /sys/class/scsi_host/host1/scanNote: You need to monitor the “issue_lip” in /var/log/messages to determine when the scan will complete.This operation is an asynchronous operation.
You can also use rescan-scsi-bus.sh script to detect new LUNS.
# yum install sg3_utils # ./rescan-scsi-bus.sh
4. Verify if the new LUN is visible or not by counting the available disks.
# fdisk -l 2>/dev/null | egrep '^Disk' | egrep -v 'dm-' | wc -lIf any new LUNS added , then you can see more count is more then before scanning the LUNS.
Scanning SCSI DISKS in Redhat Linux
1. Finding the existing disk from fdisk.[root@mylinz1 ~]# fdisk -l |egrep '^Disk' |egrep -v 'dm-' Disk /dev/sda: 21.5 GB, 21474836480 bytes2. Find out how many SCSI controller configured.
[root@mylinz1 ~]# ls /sys/class/scsi_host/host host0 host1 host2In this case, you need to scan host0,host1 & host2.
3. Scan the SCSI disks using below command.
[root@mylinz1 ~]# echo "- - -" > /sys/class/scsi_host/host0/scan [root@mylinz1 ~]# echo "- - -" > /sys/class/scsi_host/host1/scan [root@mylinz1 ~]# echo "- - -" > /sys/class/scsi_host/host2/scan4. Verify if the new disks are visible or not.
[root@mylinz1 ~]# fdisk -l |egrep '^Disk' |egrep -v 'dm-' Disk /dev/sda: 21.5 GB, 21474836480 bytes Disk /dev/sdb: 1073 MB, 1073741824 bytes Disk /dev/sdc: 1073 MB, 1073741824 bytes #multipath -ll oradata03 (360050768018085dc7000000000000xxx) dm-8 IBM ,2145 size=500G features='1 queue_if_no_path' hwhandler='0' wp=rw |-+- policy='service-time 0' prio=50 status=active | |- 1:0:0:4 sde 8:64 active ready running | `- 8:0:0:4 sdu 65:64 active ready running `-+- policy='service-time 0' prio=10 status=enabled |- 1:0:1:4 sdm 8:192 active ready running `- 8:0:1:4 sdac 65:192 active ready runningHow to remove LUN from Live Server ?
Step 1: Unmounting the LUN :
First, we need to unmount the file system we are about to release.
umount /dev/mapper/oradata03
Once unmount the filesystem now lets remove the related Logical volume, Volume group and Physical volume.
# fdisk -l /dev/mapper/oradata03
Disk /dev/mapper/oradata03: 536.9 GB, 536870912000 bytes, 1048576000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 32768 bytes / 32768 bytes
Disk label type: dos
Disk identifier: 0x77e6d4cb
Device Boot Start End Blocks Id System
/dev/mapper/oradata03p1 2048 1048575999 524286976 83 Linux
Now with fdisk you can delete the partitions .
#fdisk /dev/mapper/oradata03
Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
g create a new empty GPT partition table
G create an IRIX (SGI) partition table
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)
Command (m for help): p
Disk /dev/mapper/oradata03: 536.9 GB, 536870912000 bytes, 1048576000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 32768 bytes / 32768 bytes
Disk label type: dos
Disk identifier: 0x77e6d4cb
Device Boot Start End Blocks Id System
/dev/mapper/oradata03p1 2048 1048575999 524286976 83 Linux
Delete the Partition oradata03p1
Command (m for help): d
Selected partition 1
Partition 1 is deleted
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 22: Invalid argument.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
# partprobe /dev/mapper/oradata03
Now lets clear the Alias information from multipath.conf.
Step 2: Removing disks from the multipath config
Delete entries from multipath configuration file under alias and blacklist exceptions.
# vi /etc/multipath.conf
multipaths {
multipath {
wwid 360050768018085dc7000000000000xxx
alias oradata03
}
}
blacklist_exceptions {
wwid "360050768018085dc7000000000000xx"
}
Ahead we need to remove from the wwids file by editing or using the “multipath -w” command.
# vi /etc/multipath/wwids
# multipath -w 360050768018085dc7000000000000xxx
wwid '360050768018085dc7000000000000xxx' removed
Explain -w options ( multipath -help) :
-w remove a device from the wwids file
Flush the DM device name using -f option. from above command my dm was dm-8
# multipath -ll
# multipath -f dm-8e
Steps 3: Removing SAN paths .
Remove the device paths , from the first command of multipath -ll you see that my devices paths are sde sdu sdm sdac
Remove the devices got from “multipath -ll” or can find the device name from below location.
# ls -lthr /dev/disk/by-id/*xxx ( to get more information)
# echo 1 > /sys/block/sde/device/delete
# echo 1 > /sys/block/sdu/device/delete
# echo 1 > /sys/block/sdm/device/delete
# echo 1 > /sys/block/sdac/device/delete
This will remove the Storage device (LUN) from RHEL, CentOS, Oracle Servers and variants.
