While every HP 3PAR array starts life as a well thought out and highly designed solution, occasionally there are events that throw these arrays into a midlife crisis.  These potentially life changing events typically involve storage capacity upgrades based on available resources without taking into account the effect on the overall array’s configuration, otherwise known as being out of balance.

In my capacity as an HP Storage MASE (Master Accredited Solutions Engineer) I am certified to provide a solution to such events and recently completed an in service rebalance and capacity upgrade exercise for an enterprise client’s HP 3PAR 7400 array system that began with one node pair, two 2U cages, and two 4U cages – for a total of five cages).


If this is the first time you have heard the term “rebalance” in the 3PAR world, allow me to elaborate:

HP’s 3PAR Best Practices guide recommends that in order to get the most out of your 3PAR array in terms of performance and capacity, you want to follow certain simple although important rules to keep the array’s architecture in balance:

  • On a 4-node system, install the same drive types on both node pairs – ideally, the same count.
  • When possible, configure RAID with a high availability at the cage level, which means the array will withstand the loss of any cage.
  • Distribute the drive types evenly across all the cages, in order to avoid un-balanced configurations and potential performance issues.
  • For large-form factor (LFF) cages, avoid mixing different drive types in a single column.
  • On a 4-node system, it is particularly important to spread the SSDs across the entire system, in order to avoid hot spots due to the high performance nature of these drives.

Without rebalancing, the aforementioned array would be breaking all of these rules once the expansion was complete and could potentially cause a critical systems outage!

As with any IT project, this one was not any different; the client had a limited budget for the initial purchase, and the solution implemented was a trade-off between cost and benefit (i.e. capacity and performance).  Later on, the client wanted to expand the array, so the plan was to increase from five to the maximum supported of twenty cages thereby requiring a rebalancing of the array.

After discussing the overall capacity expansion and rebalancing plan with the client, validating applicable pre-requisites, and providing assurances that rebalancing can be performed with the array 100% online, a detailed project plan provided for their review.  The planning stage of this effort was rewarded as the actual rebalancing tasks took less than three days – with the bulk of the activities performed remotely.  Drives were relocated across the array, new node pair and cages were added, and lastly a tuning of the system was issued with all services delivered without any setbacks at all

So if you fear that your HP 3PAR array is approaching a midlife crisis, contact DTM today and we will help guide your environment back into balance!




Ozzie Castillo is the Professional Services Organization’s Practice Lead and Senior Technical Consultant for Enterprise Storage and brings over 13 years of professional IT Industry experience to DTM clients. Ozzie is an HP Master Accredited Solutions Expert (MASE) on Storage Technologies, as well as an ITIL and VMware VCP certified professional. Ozzie is a graduate of Universidad Industrial de Santander Bucaramanga, Colombia with a B.Sc., Computer Science. He has a broad experience across many different IT technologies including but not limited to: Storage/SAN, Servers, Converged Infrastructure, Operating systems (HP-UX, VMware, Linux, and Windows), High Availability, Business Continuity, and Disaster Recovery. Ozzie brings a strong expertise in the design, implementation, operation and ongoing improvement of enterprise storage solutions. Ozzies’s skills and credentials uniquely position him to deliver extraordinary value to DTM’s clients in respect to all aspects of data storage.

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