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6.2.5
Data Retention
Data Retention is another major characteristic of SSD's that must be accounted for by all the algorithms that
the SSD implements. While powered up, the Data Retention of SSD cells are monitored and rewritten if the cell
levels decay to an unexpected level. Data Retention when the drive is powered off is affected by Program and
Erase (PE) cycles and the temperature of the drive when stored.
6.2.6
Lifetime Endurance Management (Available on select models)
As stated in Section 6.2, an SSD has a limited number of Program and Erase (PE) cycles that are capable. In
worse case applications, the write workload could be such that the drive experiences a high Write Amplification
Factor that could lead to potential wear out prior to the drive achieving it's expected field life. Additionally, the
Data Retention spec of the SSD needs to be considered to ensure the spec is met once the drive is worn out.
Seagate has implemented a Lifetime Endurance Management technique which helps OEMS and user to avoid
early wear out. By monitoring the write workload being sent to the drive, the drive can add additional response
time to WRITE commands to provide a sustainable level of performance that is capable of being sustained for
the life of the drive. Most users may never see this added response time in their applications.
6.2.7
SSD Percentage Used Endurance Indicator
An application can interrogate the drive through the host to determine an estimate of the percentage of device
life that has been used. To accomplish this, issue a LOG SENSE command to log page 0x11. This allows
applications to read the contents of the Percentage Used Endurance Indicator parameter code. The Percent-
age Used Endurance Indicator is defined in the T10 document SBC-3 available from the T10 committee.
6.3
Reliability and service
Integrators can enhance the reliability of Pulsar.2 drives by ensuring that the drive receives adequate cooling.
Section 7.0 provides temperature measurements and other information that may be used to enhance the ser-
vice life of the drive. Section 11.2 provides recommended air-flow information.
6.3.1
Annualized Failure Rate (AFR) and Mean Time Between Failure (MTBF)
The production drive shall achieve an AFR of 0.44% (MTBF of 2,000,000 hours) when operated in an environ-
ment that ensures the case temperatures do not exceed the values specified in Section 7.5. Operation at case
temperatures outside the specifications in Section 7.5 may increase the product AFR (decrease the MTBF).
The AFR (MTBF) is a population statistic not relevant to individual units.
The AFR (MTBF) specification is based on the following assumptions for Enterprise Storage System environ-
ments:
• 8760 power-on hours per year.
• 250 average on/off cycles per year.
• Operations at nominal voltages.
• Systems will provide adequate cooling to ensure the case temperatures specified in Section 7.5 are not
exceeded. Temperatures outside the specifications in Section 7.5 will increase the product AFR and
decrease the MTBF.
6.3.2
Preventive maintenance
No routine scheduled preventive maintenance is required.
6.3.3
Hot plugging the drive
When a drive is powered on by switching the power or hot plugged, the drive runs a self test before attempting
to communicate on its' interfaces. When the self test completes successfully, the drive initiates a Link Reset
starting with OOB. An attached device should respond to the link reset. If the link reset attempt fails, or any
Pulsar.2 SAS Product Manual, Rev. B
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