35
System Connection
This chapter outlines the general configuration rules you should follow when cabling
a storage system. A complete description of the power-on and power-off procedures
is also given in this chapter.
General Considerations on Making Connections
When selecting the number of hard drives to be included in a logical drive, the host
channel bandwidth and the mechanical performance of individual disk drives should
be considered.
It is a good practice to calculate performance against the host port bandwidth when
designing an application topology. As an example, if eight members are included in a
logical drive and this logical drive is associated with a host ID (LUN mapping), the
combined performance of this logical drive should approximate the channel
bandwidth. If, for example, two 6-drive logical arrays are associated with two IDs
residing on a single host channel, there may be a trade-off with performance.
There are other considerations:
For example, a spare drive carries no data stripes and will not contribute to
disk-level performance. Refer to the documentation for your hard drives for
performance data.
The disk drives in the same logical drive / array should have the same
capacity, but it is preferred that all the drives within a chassis have the same
capacity.
A spare drive should have a minimum capacity that is equivalent to the largest
drive that it is expected to replace. If the capacity of the spare is less than the
capacity of the drive it is expected to replace, the controller will not proceed
with the failed drive rebuild.
When cabling, pay attention to signal quality and avoid electronic noise from
adjacent interfaces, e.g., do not lay power cords on optical cables.
Route the cables away from places where it can be damaged by other devices,
e.g., foot traffic or fan exhaust.
Do not over-tighten or bend the cables.
