HMC & CMC

Disk level validation for Live Partition Mobility (LPM) of NPIV LPAR (Logical Partition using NPIV storage via Virtual FC adapters) is a key enhancement to the LPM process. This blog is focused on providing the details of this new feature which enables better NPIV storage validation while validating Active LPM of NPIV LPAR.

Problem Statement:

Prior to this feature, validation for LPM of NPIV LPAR was limited to checking 'FC zoning', i.e. it checked if the destination server had connectivity to the same storage-ports as was connected to the source server, but did not validate 'LUN masking' to see if the same disks are connected to the migrating partition on the destination server as the source server. Now with this feature in place, validation could be used to “additionally” check 'LUN masking'. In this blog we will try to explain the feature using certain well explained figures.

Let’s start with the detailed explanation of how traditionally LPM validation of NPIV partitions worked. Then, we will discuss the validation enhancement.

What is the FC Zoning check performed as part of the existing NPIV LPAR "LPM Validation" ?

Referencing the figure above, each VM has a virtual FC adapter (i.e vfc client) with a pair of WWPNs (i.e. wwpn_c1 and wwpn_c2). Though a virtual FC adapter uses only one of these WWPNs during normal operations, the second one is required for LPM and is used on the destination server. As shown in this figure, for successful LPM operation, it is important to "zone" (at FC switch) both WWPNs to the same storage target port WWPN, i.e. wwpn_T1 and "mask" (at storage) both WWPNs to same disks (i.e. LU G and LU H).

The existing LPM validation would check FC zoning, i.e. if the alternate WWPN (i.e. wwpn_c2 -> used by migrating LPAR on destination server) has access to the same storage targets ports (i.e. wwpn_T1) as is accessed by primary WWPN (i.e. wwpn_c1 -> used by the migrating LPAR on source server). The check was limited to FC zoning and did not validate to see if the same LUNs are masked to both the client WWPNs. In this case, since the same target port wwpn_T1 is zoned to both the WWPNs of the client, LPM validation succeeds.

What is the need for the new "NPIV Disk level validation" ?

In the example figure above, alternate WWPN, i.e wwpn_c2 is mapped to incorrect disks (i.e. LU D and LU H ) instead of LU G and LU H. If the LUN masking is incorrect, there could be many problems for the migrated LPAR  such as:

• Losing access to rootvg disks

• Applications going down due to appropriate disk not being available

• Worse case, corrupting the storage disks of other partitions.

Solution:

• Provide an option to specify the disk along with port validation while validating Active LPM of NPIV LPAR.

• This feature basically identifies the difference in LUN masking for the WWPNs of the client (i.e. LU G and LU H masked to wwpn_c1, but LU D and LU H masked to wwpn_c2) and reports the mismatch so the user can take appropriate action to correct the issue.

Note : When using the option to perform disk level validation (--npivval portdisk), the validation will take little longer than usual depending on the number of FC ports/LUNs attached to the partition.

How do I use this feature through HMC ?

•  HMC version should be V8 R8.6.0 or later.

•  VIOS level 2.2.5.0 or later.

•  CLI: 

           migrlpar  -m <source managed system> -t <target managed system> -p <lpar name> | --id <lpar id> [--npivval <port/portdisk>]  -o v
           

          --npivval – Specifies if NPIV disk (along with port) validation is required or not            
           Allowed Valid values are
                    port - Only NPIV Port Validation(default)
                    portdisk - Both NPIV Port and disk 

• Rest API :          

What does the validation error message look like if disk validation for LPM operation failed ?

Pasted below is a snippet of the sample validation failure output, through the HMC CLI interface, when User tries to validate LPM where different set of LUNs were masked for both the WWPNs of the migrating LPAR.

migrlpar  -m z2230be -t z2230ae -p lpmftclp092  --npivval portdisk  -o v

.. .. .. output truncated .. .. ..

Errors:
HSCLA319 The partition's virtual Fibre Channel client adapter 292 cannot be hosted by the existing Virtual I/O Servers (VIOSs) on the destination managed system.  Set up the necessary VIOS host on the destination managed system, then try this operation again.

Details:
HSCLA356 The RMC command issued to partition z2230ap1 failed.  This means that destination VIOS partition z2230ap1 cannot host the virtual adapter 292 on the migrating partition.
HSCLA29A The RMC command issued to partition z2230ap1 failed.
The partition command is:
migmgr -f find_devices -t vscsi -C 0x3 -a ACTIVE_LPM -M 1 -d 1
The RMC return code is:
0
The OS command return code is:
83
The OS standard out is:
Running method '/usr/lib/methods/mig_vscsi'
83

VIOS_DETAILED_ERROR
Executed find_devices on VIOS 'z2230ap1' (hostname: z2230ap1.rch.stglabs.ibm.com)
Client Target WWPNs: 5005076801102d6f 5005076801402d71
Skipping FC adapter in validation because FC adapter fcs1 is not NPIV capable
domain_id for fscsi0 is: 84
Found target WWPN=5005076801102d6f with SCSI_ID=530300
Found target WWPN=5005076801402d71 with SCSI_ID=530700
Target 0x5005076801102d6f found
Target 0x5005076801402d71 found
Matched 2 targets, source has 2 targets, destination has 2 targets

List of Logical Units not found on destination ( i.e. NOT masked on storage target port = 0x5005076801102d6f with client's alternate wwpn = 0xc0507606930500c9; but masked with client's source wwpn = 0xc0507606930500c8 ) :
Logical Unit 1 : descriptor type = 3, value = 600507680195016B7800000000000269.
Logical Unit 2 : descriptor type = 3, value = 600507680195016B78000000000002F5.
Logical Unit 3 : descriptor type = 3, value = 600507680195016B78000000000002F6.

List of Logical Units found additional on destination ( i.e. masked on storage target port = 0x5005076801102d6f with client's alternate wwpn = 0xc0507606930500c9, but NOT masked with client's source wwpn = 0xc0507606930500c8 ) :
Logical Unit 1 : A non-disk type device.

List of Logical Units not found on destination ( i.e. NOT masked on storage target port = 0x5005076801402d71 with client's alternate wwpn = 0xc0507606930500c9; but masked with client's source wwpn = 0xc0507606930500c8 ) :
Logical Unit 1 : descriptor type = 3, value = 600507680195016B7800000000000269.
Logical Unit 2 : descriptor type = 3, value = 600507680195016B78000000000002F5.
Logical Unit 3 : descriptor type = 3, value = 600507680195016B78000000000002F6.

List of Logical Units found additional on destination ( i.e. masked on storage target port = 0x5005076801402d71 with client's alternate wwpn = 0xc0507606930500c9, but NOT masked with client's source wwpn = 0xc0507606930500c8 ) :
Logical Unit 1 : A non-disk type device.

Logical Units masked for the client on the WWPN of source = 0xc0507606930500c8 and destination = 0xc0507606930500c9 did not match. Please correct the LU masking from Storage and retry.
End Detailed Message.
The OS standard err is:
.. .. .. output truncated .. .. ..

Summary

Customers have asked for assurance that if LPM validation passes then LPM should also succeed. Disk level LPM validation enhancement to detect incorrect LUN masking with NPIV was added to narrow the scenarios where LPM validation passes but LPM fails. 

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