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I am trying to configure my HP MSA 2012i such that every disk is a vdisk and every vdisk is a volume. Each volume shall be accessible using iSCSI. So each volume shall be a iSCSI target. This is not a raid, I rather want to use the single disks.

I have 12 disks in this device. So I get 12 vdisks and consequently 12 volumes.

Do I have to assign each volume a different LUN? If I discover the target, what would the output of multiple LUNs look like?

My OS is Ubuntu and I am using open-iSCSI. There is also multipath installed but physically disabled. I have pulled the plug of one of the two cables.

The main problem is that the iSCSI initiator can only find one target, not all 12. To be more specific, the initiator finds always one target but after performing the iSCSI login, there are new devices in /dev/sd* if and only if I exported the first disk (with the id 0.0, the disk in the upper left corner of the array). If I don't export the first disk, then there is no new entry in /dev/sd*. If I export the first disk, there is a new entry corresponding to the first disk. It does not depend on whether there are other exported disks.

I don't have any clue.

Could the initiator be the problem? What would I have to do to discover multiple LUNs?

Edit:

# show volume-maps 
Volume [SN <num>, Name (volume00)] mapping view:
CH       ID LUN Access Host-Port-Identifier                    Nickname        
-------------------------------------------------------------------------------
0,1       0  15 rw     all other hosts                          

Volume [SN <num>, Name (v11)] mapping view:
CH       ID LUN Access Host-Port-Identifier                    Nickname        
-------------------------------------------------------------------------------
0,1       0  11 rw     all other hosts                          

Volume [SN <num>, Name (v01)] mapping view:
CH       ID LUN Access Host-Port-Identifier                    Nickname        
-------------------------------------------------------------------------------
0,1       0   0 rw     all other hosts                          

Success: Command completed successfully
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Why are you doing it this way? Can you give some more background? –  ewwhite Aug 1 at 22:53
1  
I want to use ZFS as the file system. So the initiator should get the disks and manage ZFS. ZFS can build a raid on it's own. –  A. Res Aug 1 at 23:01
    
Is this an experiment, or do you intend to use this with real data in production? –  ewwhite Aug 2 at 11:44
    
Why aren't you using DAS for this? This is a very unusual setup that you're going for. –  MDMarra Aug 2 at 13:46
1  
It would not be an experiment. I intended to use this for data in production. DAS would solve all my problems, but I have the device ( HP MSA 2012i ) and I don't have the hardware for a DAS. I decided to use the MSA as it should be: I will create one big vdisk, consisting of all real disks (some as spares), and one volume and export this. So I don't use the capabilities of ZFS for Raid. Thank you all for your fast support. –  A. Res Aug 3 at 8:44

1 Answer 1

up vote 4 down vote accepted

This is a bad idea...

Sometimes it makes sense to use ZFS with hardware RAID, or a combination of ZFS and hardware RAID. This is one of those cases.

The main issue you'll encounter doing this the way you're planning is that each single disk will be its own VDISK and have its own MSA RAID metadata. The failure of a disk means that the VDISK is completely faulted. This has an impact on hot swap capabilities, as you'll need to destroy that LUN and create a new one just to replace a disk.

Think about this, especially since you're using iSCSI (and 1Gbps at that!). Create the RAID level you want using the MSA's built-in RAID functionality. If you want some ZFS management, break it into hardware RAID mirrors of 2 disks, striped at the ZFS level. That will still give you protection, alerts, but save some of the nifty ZFS RAID features.

Do NOT create a bunch of RAID 0 arrays and think that's the same as feeding a raw disk to ZFS.

Further reading:

ZFS SAS/SATA controller recommendations

HP P410 RAID CARD Issue - unassigned drives not detected by the OS

ZFS best practices with hardware RAID


By the way, if you want to force this to work, you may be running into a controller ownership issue, and a LUN presentation issue. Did you map the iSCSI LUNs? What's the output of show volume-maps on the MSA's CLI?

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