Shocking… IBM i Cost of Storage beyond the CEC: EXP24S or V3700 SAN?

As data, and company’s overall demand for data increases at a staggering rate, many of my IBM i customers who have always relied solely on the internal storage capacity of their base server (Also known as the CEC), are being forced to expand outside of their IBM Power System chassis.  I believe this has been driven not only by the pure, raw storage needs of the business but in some cases, more importantly, the I/O needs of the business.  IBM i does a great job of balancing reads and writes across all disk but when you get into a position where your disk can’t keep up, it can really hinder overall performance.  To learn more about disk constraints, check out my blog post “Out growing your IBM Power system internal disk? Expansion drawer or Bigger Drives?“.

Other customers have already embraced growth outside of the 4U internal server storage (CEC) and are now looking to optimize it. This crossroads for companies running business critical applications with IBM i, on IBM Power Systems infrastructure has become a main focus and quite possibly an obsession for me.  Fortunately for me, I work with some of the best IBM i engineers in the country who stay on the leading edge of IBM i and Power Systems technology.  I love to learn, they love to teach, and the more I learn the busier both of us get. At the end of the day, I know that price is important for my customers.  As a result, I study pricing to bring additional value to the overall config process, just as my engineers focus on hardware and software functionality.

The rest of this article will focus on two different options for growth beyond the CEC. 

OPTION 1: The first option is the traditional EXP24S or 5887 DAS (Direct Attached Storage) expansion drawer.  This unit is 2U’s and can support up to 24 SFF2 disk drives in a single unit.  All processing and management is done through IBM i.

OPTION 2: The second option is the IBM Storwize V3700 SAN. The V3700 SAN is an entry level hybrid storage system that’s built on the innovative technology found at all levels of the IBM Storwize family.  The Storwize V3700 addresses block storage requirements for midsize businesses.

Is internal storage expansion really the most cost effective option for IBM i?

Due to my responsibilities as an IBM business partner, I am sticking with list pricing to compare the two disk expansion options.  Though I can only use list pricing for my review, you may find that your business partner has a bit more wiggle room on the SAN pricing than on Internal disk because of the competitive landscape within the SAN storage world. SAN storage competes in a much wider marketplace due to it’s cross platform makeup. Before we look at the comparison, it’s important to look at the numbers for each of the two scalable storage options.  Both options are built to support redundancy through the elimination of single point of failure.

EXP-24S (5887 drawer)

Note the dual EJ0L PCIe3 RAID cards with 12GB Cache.  The older #ESA3/5913 PCIe Gen-2 predecessor was withdrawn but is still usable on Power8. The “only” remaining high-performance RAID controller (beyond the one in the enhanced backplane) is the PCIe3 12GB Cache (#EJ0L). A pair of adapters are required to provide mirrored write-cache data and adapter redundancy.  With 12GB of RAID Cache, it just makes sense for IBM i workloads.  The EJ0L cards can also support up to 4 EXP-24S drawers so they offer a deeper level of scalability in a single PCIe3 card then the previous 5913.  So, you will see that I included dual EJ0L cards in the pricing table for the EXP-24S.

IBM Storwize V3700 SAN Controller & Expansion

Note: ACHK 8gb FC port cards have been added to each side of the V3700 controller for making the SAN to Switch connection.  Dual Fibre switches for redundancy give us the ability to build and manage virtual fiber connections to external storage.  Dual 5729 PCIe2 8GB Fibre Adapters installed in the Power8 to make the connection from Power8 to Fibre switch SAN24B-24.

My price comparison focused on the total cost per drive, starting at drive 5 (Raid set of 4 + 1 Hot Spare).  I continued the analysis through the 8^th drawer or 192 drives.  The IBM datasheet says the V3700 can run a max of 240 drives or 10 drawers, but decided to stop at drawer 8 due to internal storage needing another pair of EJ0L Raid cards which would require a PCIe expansion drawer.  That would add some unnecessary complexity to the analysis that I didn’t want to take on.

I know SAN is a viable solution for IBM i just based on the many benefits external storage brings to the management, processing, and continuity of data.  It was a big surprise to find how quickly the larger upfront cost of the SAN was offset by the higher cost/drive for internal disk.  As you can see on the above diagram (YELLOW box), the SAN option transitions to the more cost effective storage solution at drive 58.  Without even touching on the many benefits SAN brings to the table for IBM i, it has a quick disk to disk return to the IT bottom line.

Additional Considerations

• If you’re looking to incorporate SSD’s in the expansion stack you should be aware that all SSD’s in the EXP-24S will carry a fairly hefty annual maintenance cost, while SSD’s in the V3700 are covered under standard support.  
• Another thought on the utilization of SSD’s to increase i/O performance.  While IBM i provides tools to assist you in placing heavily used data onto SSDs and allows tagging of objects to be placed on SSDs, Storwize with EasyTier makes those decisions for you on the fly, removing another administration function from your list.”
• The Storwize V3700 SAN offers the benefit of flash copy which offers a huge benefit for customers open to virtualization and running VIOS.  In a nutshell, you can utilize flash copy to build exact copies of production for test/dev use and shrink your backup window down to less than 12 seconds.
• If you add Remote Mirror you can replicate to an offsite location from SAN to SAN, taking the burden off the server itself.  This paired with IBM’s PowerHA brings even more benefits for building out solid continuity solutions.