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Controller card and disk drive orientation for maximizing electrical performance and reducing cost within a storage enclosure

IP.com Disclosure Number: IPCOM000032893D
Original Publication Date: 2004-Nov-17
Included in the Prior Art Database: 2004-Nov-17
Document File: 5 page(s) / 2M

Publishing Venue

IBM

Abstract

State of the art Fibre Channel Disk Drive enclosures (either RAID or Storage Expansion) are designed to support high speed electrical signaling rates of 2Gb/s (FC-AL interfaces) with 4Gb/s following close behind. These high speed interfaces communicate information between the controller cards and all of the disk drives (current best case density is 16 HDDs in 3U (5.25"). To complicate matters a high speed interface, such as PIC-X, may also be required between the controller cards for controller-to-controller communication. All of these requirements dictate an optimal positional interdependency amongst all the drives and controller cards. A Fiber Channel Disk Drive enclosure has been designed to address the total set of these requirements with an optimum location and orientation of disk drives and controller cards as well as an internal midplane. Such an implementation is also key to incorporating future disk drive technologies (e.g. 4Gb/s) and higher bandwidth controller card functions which require absolute minimum net lengths.

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Controller card and disk drive orientation for maximizing electrical performance and reducing cost within a storage enclosure

Typical disk drive enclosures orient the disk drives vertically,
from left to right anywhere from 14 to 16 HDDs across, or
horizontally with four rows of four abreast, all in the rear of
the enclosure. In the front of the enclosure the controller
cards are typically located either on the extreme ends, one to
the left and the other to the right, or side by side in the
middle. Neither of these are optimal to meet the aforementioned
needs. In some cases the controller cards are oriented
horizontally but usually one on top of the other, again, this is
suboptimal since this will unnecessarily "stretch" the high speed
net traces on the midplane. This may be acceptable for some
2Gb/s midplane designs but to support 4Gb/s and beyond the extra
net lengths will result in unacceptable signal degradation,
further necessitating more exotic midplane material to mitigate
the lack of signal integrity.

Figures 1-3 illustrate several different enclosure layouts that
are sub-optimal.

Figures 4a & 4b illustrates how an optimal enclosure locates and
orients the aforementioned critical system components. Figure 5
illustrates how the controller card connectors are optimally
situated amongst all the 16 disk drive connectors.

Referring to figure 4b, the two redundant controller cards are
horizontally positioned one above the other but separated by some
distance. This distance is a tradeoff amongst electrical
connections between the each controller card and all the disk
drives within the enclosure as well as the electrical connections
between the two controller...