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Dynamically increasing the size of a SAN LUN

Product Documentation


Abstract

Starting in 7.3 TR3 (and later releases), the size of a configured SAN disk unit can be increased dynamically on Spectrum Virtualize based storage products (such as SVC, V7000, etc.)
Starting in 7.3 TR7 and 7.4 TR1 (and later releases), the size of a configured SAN disk unit can be increased dynamically on DS8900.

Content

Increase of virtual LUN size after initial allocation

External storage systems have the capability to increase a LUN size after its initial allocation. In the past, IBM i has not viewed any increase in a LUN’s size on an external storage system. Additional LUNs needed to be added to increase the capacity of a logical partition.

With IBM i 7.3 TR3 (and later releases), IBM i will recognize that an increase has occurred for Spectrum Virtualize based storage products. After an IPL, will allow the LUN to be used at its newly increased size.

As of 7.3 TR7 & 7.4 TR1 (and later releases), IBM i now supports the changing of the size of a LUN that comes from a DS8900 storage controller.  If the LUN type on a DS8900 is a variable LUN size (models 050 and 099), that LUN can increase in size. 

The IBM i host will not fully recognize the size change immediately, yet begins processing to prepare the internal structures for the size increase.  After the next IPL, the full capacity of the new LUN size is usable.  This can be utilized on all disks, including the the load source.

Additional details -

  • LUNs formatted with 4096 byte sectors will not change size.  Dynamic increase of LUN size is only supported for 512, 520 and 4160 byte sector formats.
  • Reduction of LUN size is NOT supported.
  • If a mirrored LUN is increased, the change will not be recognized by IBM i even after an IPL.  For IBM i to recognize an increase in the size of a mirrored LUN, do the size increase and then stop mirroring on IBM i, IPL IBM i past storage management recovery for the new larger size to be recognized, and then start mirroring again.
  • The System Service Tools Advanced Analysis command GETDILSSTATUS will show if a LUN size change is in progress:
STRSST and sign in
Option 1. Start a service tool
Option 4. Display/Alter/Dump
Option 1. Display/Alter storage
Option 2. Licensed Internal Code (LIC) data
Option 14. Advanced analysis
Enter the following data:
    1      getdilsstatus
   Press Enter
Leave the Options as [blank] and press enter
  • If the system is IPL'd before the additional storage has been initialized, it will resume initialization after the IPL has gone through SM recovery, and will require another IPL after the initialize is complete in order for the OS to show and use the larger size.  Use GETDILSSTATUS to check before an IPL.
  • The following LIC log entries may be associated with increasing LUN size:
Major-Minor Description
1000-5111 Data needed to be moved and completed successfully
1000-5112 Data needed to be moved, but failed to move
1000-5113 Initialization of the additional storage completed successfully
1000-5114 Initialization of the additional storage failed
Steps for High Availability iASP environments:
1) Required PTFs:
    1a. IBM i 7.4 - Technology Refresh 1 needs to be applied. MF66481 is recommended.
    1b. IBM i 7.3 - Technology Refresh 7 and PTF MF68678 need to be applied. MF66474 is recommended.
    1c. IBM i 7.2 and below - Dynamic Lun Expansion is not supported. Volume will need to be removed from ASP, unmapped, increased, remapped, re-added to ASP.
2) Expand source and target node LUN's on storage.
3) Ensure that the iASP is Varied On and Available at the source node to allow the volume to be prepared.
    DSPASPSTS ASPDEV(xxxxx), where ASPDEV is the iASP device which can be found with WRKASPCPYD command.
        If the iASP is not varied on, then use the following command where xxxxx is the iASP device:
            VRYCFG CFGOBJ(xxxxx) CFGTYPE(*DEV) STATUS(*ON)
4) Allow prepare to complete on source - this can be monitored with getdilsstatus macro:
    4a. STRSST and sign in
    4b. Option 1. Start a service tool
    4c. Option 4. Display/Alter/Dump
    4d. Option 1. Display/Alter storage
    4e. Option 2. Licensed Internal Code (LIC) data
    4f. Option 14. Advanced analysis
    4g. Enter the following data:
        1      getdilsstatus
       Press Enter
    4h. Leave the Options as [blank] and press Enter
5) Vary off the source node iASP and then vary back on the source node iASP to complete the disk expansion on the source node:
    VRYCFG CFGOBJ(xxxxx) CFGTYPE(*DEV) STATUS(*OFF)
    VRYCFG CFGOBJ(xxxxx) CFGTYPE(*DEV) STATUS(*ON)
6) IPL the target node for storage management to repopulate the target node disk sizes.
    *Note: without completing this step, the flashcopy will fail.
7) Perform the iASP Flash Copy - Vary on of target iASP is expected to complete normally and additional prep is not needed since its copied from the source.

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Document Information

Modified date:
08 March 2022

UID

ibm10716777