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San disk appearing double in old AIX

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Operating Systems AIX San disk appearing double in old AIX
# 1  
Old 08-06-2014
DB San disk appearing double in old AIX

Hi guys, Smilie

I'm a studient in IT field (AIX)

I'm trying to map a LUN from a SAN (DS3400) to an AIX server (5300-04-00)

I know there is no MPIO on this version of AIX, and i see double my LUN from the SAN

root@localhost # lscfg | grep hdisk
+ hdisk7           U787F.001.DPM35ZF-P1-C1-T2-W202400A0B868BF73-L0  fcparray Disk Array Device
+ hdisk8           U787F.001.DPM35ZF-P1-C1-T1-W202300A0B868BF73-L0  fcparray Disk Array Device

My senior told me there is a method for have an MPIO like.

Any one know how i can to that Smilie

Thanks for your help, and sorry for my english (from FRANCE) Smilie
# 2  
Old 08-06-2014
Do you get any output from the command:-

If you do, what you might well have is hdisks being collected together to form a vpath device. It is this device that you assign to your volume groups.

Does this help?

# 3  
Old 08-06-2014
To expand on what rbatte1 said: when connecting virtual disks (LUNs) from a SAN to a system one usually has a "fabric" in between. Such a fabric is basically a FC-switch, redundant adapters/FC-lines to connect to the storage system (DS8000, EMC VMax, ....) and the clients (basically your systems).

Simple "hdisk"-devices are usually representing one such path over which a disk can be seen, but there might be several parallel ways to see the disk:

|  host           | 
   |       |
   | 3     | 4
   |       |
|  FC-Switch      |
   |       |
   | 1     | 2
   |       |
|  Storage        |

Here a single disk from the storage can be seen over line 1 then 3, 1 then 4, 2 then 3 or 2 then 4, so you'd have 4 hdisk devices which are just different views onto the same object. (Consider 4 pictures showing the same building but from different angles.) Multipath-drivers (MPIO, SDD, EMCs Powerpath, etc.) now bind together all these views to a usable pseudo-device representing the real disk behind all these. Depending on the driver they are named differently - vpath devices, powerpath devices, but the concept is the same.

I hope this helps.

# 4  
Old 08-06-2014
Thanks for ur reply, i'm not at office right now.

I forgot to told u there is no switch beetween san and server, its directly connect.
# 5  
Old 08-06-2014
Originally Posted by Tharsan
I forgot to told u there is no switch beetween san and server, its directly connect.
You still could have 2 redundant FC-adapters which is probably why you see the disk twice - once over each adapter.

I hope this helps.

# 6  
Old 08-06-2014
Let's hope that the fibre ports in use at each end are not on the same card. Someone has done that here and which we're protected against the fibre cable failing, a failure in the port cannot be fixed without downtime, and a failure of the card causes downtime.

# 7  
Old 08-06-2014
I have one card with dual FC port. What i'm trying to do is 2 paths trough each controller to access the same LUN. Then if one of the controller crash, i can still access the LUN with the other one.

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