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Linux add lun and expand on EMC CX4-120

Posted on 2009-12-28
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Last Modified: 2013-12-06
Dear Sirs,

I have an EMC CX4-120 with a Linux host 2.6 kernel connected with 3 luns and working fine.

I have 2 questions :

1- How can I add a LUN without rebooting the linux host

2-How can I expand the size of a lun (linux ) if using striping or concatenation  method

Best Regards,
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Question by:jeanmonline
9 Comments
 
LVL 14

Expert Comment

by:cjl7
ID: 26130540
Hi,

I assume you are running lvm and you have a volume-group called vg00 and you have more then one path to the disks (running multipath)... ;)
 
to solve problem 1 (you might have other numbers on your fc_controller 1,2,3,4...):
echo "- - -" > /sys/class/scsi_host/host0/scan
partprobe
multipath


vgextend vg00 /dev/mapper/mpathXX

Question 2, IMO:
dont resize LUN's (block devices), create more instead. Then use LVM to extend and add disk where you want/need it.

Let me know some more details and I'll give you a better step-by-step.

Regars

Jonas

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Author Comment

by:jeanmonline
ID: 26130619
HI,

I have an EMC CX4-120 using the FC connection with 4 paths and powerpath as software

My question number one is:

How can I add HDD/ LUN/Additional disk from the storage without the need for reboot

Pls tell me what more infos you need for this question

My question number two is:

I have a LUN/HDD already connected to the linux host and have expand it using the Navisphere GUI from EMC (expand than use striping or concatenation ) but the problem is I cannot see it on the linux the expanded partition

Pls tell me what more infos you need for this question

BR,
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LVL 4

Expert Comment

by:thribhu
ID: 26135605
Can you tell what what HBA cards you use.(Qlogic or Emulex)

Second Question:Do not expand lun using stripe, you will loose existing data.So  better option is to expand the lun using concatination.Will not loose existing data doing this.If you have a volume manager, better add a new lun.

In case you want only striped lun to be expanded. Curve a new lun bigger that you need, use lun migration from navishpere to migrate data to new big lun from old small lun;Migration is block level and no downtime required during migration.But lun migration will take long time(nearly 2 to 3days) depending on lun siZe.

Use the Expand wiZard on right side of the navisphere.
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LVL 4

Expert Comment

by:thribhu
ID: 26135613
Mostly this should work if you are using 2.6 kernel

$ echo "scsi add-single-device 1 2 3 4">/proc/scsi/scsi

Where,

1 - HBA number
2 - channel id on the HBA
3 - SCSI ID of the new device
4 - LUN of the new device
You need to replace 1,2,3,4 with actual values or parameters as per above list.
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Expert Comment

by:thribhu
ID: 26135636
# cat /proc/scsi/scsi

check this path for these(1,2,3,4) values that are existing already.

# echo "scsi add-single-device 1 2 3 4">/proc/scsi/scsi

Where,

1 - HBA number
2 - channel id on the HBA
3 - SCSI ID of the new device
4 - LUN of the new device
You need to replace 1,2,3,4 with actual values or parameters as per above list.

Run

#Powermt config to check the paths.

If you use Qlogic HBA you can use the utility from q-logic ql-dynamic-tgt-lun-disc-1.8.tgz will discover new luns targets dynamic.

0
 

Author Comment

by:jeanmonline
ID: 26136230
Hi ,

The hbas are emulex and I have already used the striping method to expand the LUN and not the concatenation and have no free space left

Please help
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Expert Comment

by:thribhu
ID: 26138724
So did you expand the lun already and not able to discover it in the OS?
Expanding a striped lun with stripe method will loose the old data .
You can expand a striped lun with concatination method, keeps your old data.

Can you tell me what exactly are you looking for, did you try the above commands for discovering the luns in your linux 2.6 kernel OS.?

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Accepted Solution

by:
jeanmonline earned 0 total points
ID: 26142759
hi

i expanded the stripped lun without loosing data and able to add lun without rebooting but without using any of the above recommendation

tx
0
 

Expert Comment

by:naranjos
ID: 26442382
Can you provide details on whatsolution you finally used?  We have the same issue - need to expand an EMC LUN without having to restart the Linux server that mounts it.

Thanks!
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