A Better Alternative to High Port Count RAID Add-in Cards

What are the Top Five Key Benefits of Expander Boards?
What is an Expander Board?
Servers with more than 8 drives typically include either a high port count RAID add-in card, or a standard RAID adapter
and an expander. Both of these options provide increased connectivity for internal drives. Yet an expander board is often
much more affordable than a high port count RAID card, while allowing exibility in the solution architecture.
An expander board is basically a “switch” that manages inputs from more than 8 target devices, allowing all of these
devices to communicate with a 4 or 8 port SAS or RAID initiator device simultaneously. It often provides 24 or 36 ports,
which enable the connection of between 20 to 32 directly attached SAS or Serial ATA (SATA) devices; plus one SAS or
RAID adapter card.
While a common misconception is that expanders reduce performance, the opposite is true; expander boards enable a
RAID controller to achieve optimal performance. To conrm this, just check any RAID performance whitepaper. It will show
that one or more expanders are included in the tested conguration. For example, Intel’s RAID Controller RS3DC080
achieved its maximum throughput of near 6000MB/s when connected to a large number of hard-disk drives through an
expander
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Expander boards can be designed with a narrow form factor design, that can be mounted on a chassis wall or duct. Power
is obtained by using a power cable with a standard 4-pin power connector. Some expanders include PCIe “ngers” so that
they can be mounted in a standard PCIe slot and obtain power from this slot.
Cost Savings
One of the key benets of expander boards is cost savings since they provide the ability to
save hundreds of dollars compared to a high port count RAID card.
Flexibility
Expander boards also provide high exibility by allowing systems to scale from 4 to 24 or
more drives with the only change in hardware being the expander.
Reliability
Since high port count RAID cards can get very hot, they often require extra attention to cool
properly. A separate expander board reduces the power required by the RAID card. Also, the
expander can be mounted in a location that does not create thermal challenges.
Choice
Expander boards offer the choice to use the SAS or SAS RAID card desired.
Scalability
Expander boards offer room to grow. Expanders can be added when needed and they don’t
need to be replaced even if a RAID card is upgraded.
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