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SSDs Boost Performance

It’s time to consider using solid state drives (SSDs) instead of traditional hard disk drives (HDDs) for your POWER7 system disk requirements. SSDs offer superior read and write performance and are well suited for use as system drives on highly virtualized Power Systems servers. IBM Power Systems SSDs feature enterprise multi-level cell (eMLC) technology, which greatly enhances their reliability while reducing cost per GB. These SSDs are designed to handle write-intensive workloads for at least five years.

SSD Implementation Options

There are three primary options for implementing SSD technology with POWER7 servers:

  • Internal, SAS bay-based SSDs, which plug into the same slots as traditional SAS HDDs. These SSDs are available with 177 GB capacity per SAS drive bay.
  • A special function PCI Express (PCIe) SAS adapter card that supports on-the-card mounting of up to four 177 GB SSD modules.
  • SSDs placed into the SAS drive bays of external I/O drawers, which are attached to a server.

Note that SSD drives placed in the internal bays and I/O drawers are hot swappable, while SSD modules placed on the PCIe SAS card are not. We’ll focus on the first option, which most closely mimics the current use of HDDs as system disk drives.

Internal system drives are most commonly used for:

  • Virtual I/O server (VIOS) partition boot
  • Virtualized client LPAR boot
  • Dedicated server OS boot

The price per GB for SSDs has significantly dropped over the past three years. In 2009, SSDs were 21 times more expensive per GB than HDDs. Today, they’re only six times more expensive per GB. A dual VIOS implementation typically requires just four drives. For virtualized servers with a large number of LPARs, using SSDs—coupled with an enhanced cache SAS adapter—should be considered for VIOS partition boot drives. The superior performance of the SSDs over HDDs can improve performance for VIOSs.

Charlie Cler supports customers in a solutions-architect role at Forsythe Technology Inc. He can be reached at

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