Ultrastar 7K2
HGST Hard Disk Drive Technical Reference Manual
25
Hot Plug Support
SATA supports hot plugging (also known as “hot swapping”), the ability to swap out a failed hard drive
without having to power down the system or reboot. This capability contributes to both data availability
and serviceability without any associated downtime, making it a critical feature for extending SATA into
enterprise applications.
The drive supports hot plugging only in systems where a SATA hard drive storage backplane is used. The
SATA 3.0 specification requires staggered pins for both the hard drive and drive receptacles.
Staggered pins mate the power signals in the appropriate sequences required for powering up the hot
plugged device. These pins are also specified to handle in excess of the maximum allowed inrush current
that occurs during drive insertion. SATA-compliant devices thus need no further modification to be hot
pluggable and provide the necessary building blocks for a robust hot plug solution, which typically
includes:
Device detection even with power downed receptacles (typical of server applications).
Pre-charging resistors to passively limit inrush current during drive insertion.
Hot plug controllers to actively limit inrush current during drive insertion.
Active LED Status
The drive supports external LED requirements. It provides an activity LED output which is ON during
command execution and OFF otherwise.
Fluid Dynamic Bearings (FDB)
Bearing design that incorporates a layer of high-viscosity lubricant instead of ball bearings in the hard drive
spindle motor. As an alternative to conventional ball bearing technology, FDB designs provide increased
non-operational shock resistance, speed control, and improved acoustics.
Staggered Spinup and Activity Indication (SATA Power Pin 11)
Note:
This feature is available for specific OEM configurations.
SATA device power connector pin 11 is defined as a means by the host to DISABLE staggered spinup and
it may also be used by the device to provide the host with an activity indication. According to the SATA
spec, "Staggered Spin-up Disable and Activity Signal shall not be enabled at the same time."
Staggered Spinup
When multiple disks are installed in an enclosure, it is desirable to provide a simple mechanism by which
a subsystem controller can sequence hard drive initialization to minimize the current load presented
during power up. Staggered spinup provides this mechanism by preventing the hard drives from spinning
up until after successful PHY initialization (i.e., after PHY enters DP7:DR_Ready state).
Staggered spinup is only applicable during initial power-up. If a drive is spun down using ATA
commands—as a result of having been placed in Standby or Sleep power modes, for example—the
drive shall spin up following the rules that govern spinup from low power modes described in ATA/
ATAPI-6 or later.
Activity Indication
The host controller through SATA power pin 11 may access storage device status and activity. The signal
provided by the device for activity indication is a low-voltage low-current signal. It is not suitable for
directly driving an LED. A buffer circuit external to the device must be employed to drive the LED.
The activity signal is based on an open-collector or open-drain active low driver. The device shall tolerate
the activity signal being shorted to ground.
