Expand Your Horizons: Dynamically Increase the Size of your SAN Disks

One of the great advantages of using external storage has been to order your disk storage in bulk and then increase storage on your systems over time without the need to order and install new disk units. In the past, we’ve been able to add additional disk units to IBM i to increase storage. This was followed by a bit of time to add the disks to the ASP and allow the data to balance between the existing disk units and the newly added units. 

A dilemma then approaches when you hit IBM’s best practice for the number of disk units in a fiber channel host connection for IBM i – which still stands at 32 units. If you follow that best practice, which we recommend, you will need to go through the task of creating new virtual fiber channel connections, do the SAN zoning, and create a new host connection on the SAN. For many, this is not a simple task and may require hiring someone to carry out the task. 

A relatively new solution that has come to IBM i users that keep current is the ability to expand the size of your existing disk units from DS8900, Storwize, and FlashSystems products. Instead of creating and adding more disk units, you just expand the size of your current disk units. The Storwize and Flashsystems products, which utilize Spectrum Virtualize, just need to be at IBM i 7.3 TR3 and later versions. DS8900 needs to be at IBM i 7.3 TR7 and 7.4 TR1 and later versions to take advantage of this. Once IBM has informed you that all disk units are prepared, you just need to IPL the system in order for IBM i to then see the additional storage. 

Depending on the version of Spectrum Virtualize you’re using, when right-clicking on a volume you will either see Modify Volume Capacity or Expand. Both will take you to the screen to expand the size of the selected disk unit. In this example screenshot, 100 GB is being added to add to increase the size from 100 GB to 200 GB.  NOTE:  The option to Shrink is not supported in IBM i! 

Expand Your Horizons: Dynamically Increase the Size of your SAN Disks.

Once you’ve told each disk unit to expand, you can view the progress inside of System Service Tools by going to the Advanced Analysis menu. The command to use is GETDILSSTATUS. This will eventually tell you when all disk units have been prepared – signaling it’s time for an IPL. 

Expand Your Horizons: Dynamically Increase the Size of your SAN Disks.

Expand Your Horizons: Dynamically Increase the Size of your SAN Disks.

After the IPL has been completed, you can use a command like DSPSYSSTS to verify the storage has increased as expected. 

There are a few other considerations to be aware before you plan this, and a few things to be aware of in iASP environments with PowerHA. Full details can be found in this article from IBM:  https://www.ibm.com/support/pages/node/716777 

Definitely consider this option when planning to increase storage on your systems! 

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