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5.4 Checking Operation after Installation and Preparing the HDDs for Use
5.4.3
Setting parameters
The user can specify the optimal operation mode for the user system environments by setting the
following parameters with the MODE SELECT or MODE SELECT EXTENDED command:
•
Error recovery parameter
•
Caching parameter
•
Control mode parameter
With the MODE SELECT or MODE SELECT EXTENDED command, specify 1 for the "SP" bit on
CDB to save the specified parameter value on the disk. This enables the HDDs to operate by using
the parameter value set by the user when power is turned on again.
When the parameters are not set or saved with the MODE SELECT or MODE SELECT
EXTENDED command, the HDDs set the default values for parameters and operates when power is
turned on or after reset. Although the HDD operations are assured with the default values, the
operations are not always optimal for the system. To obtain the best performance, set the parameters
in consideration of the system requirements specific to the user.
This section outlines the parameter setting procedures. Refer to Subsection 4.1.4 "MODE
SELECT (15)", 4.1.5 "MODE SELECT EXTENDED (55)" of the SAS Specifications for further
details of the MODE SELECT and MODE SELECT EXTENDED commands and specifying the
parameters.
1.
At factory shipment of the HDDs, the saving operation for the MODE
SELECT parameter is not executed. So, if the user does not set
parameters, the HDDs operate according to the default value of each
parameter
2.
The model select parameter is not saved for each Loop ID of but as the
common parameter for all INIT. In the multi-INIT System, parameter
setting cannot be changed for each INIT.
3.
Once parameters are saved, the saved value is effective as long as next
saving operation is executed from the INIT. For example, even if the
initialization of the disk is performed by the FORMAT UNIT command,
the saved value of parameters described in this section is not affected.
4.
When the HDDs, to which the saving operation has been executed on a
system, are connected to another system, the user must pay attention to
that the HDDs operate according to the saved parameter value if the
saving operation is not executed at installation.
5.
The saved value of the MODE SELECT parameter is assumed as the
initial value of each parameter after the power-on, the RESET condition..
The INIT can change the parameter value temporary (actively) at any
timing by issuing the MODE SELECT or MODE SELECT EXTENDED
command with specifying "0" to the SP bit in the CDB.
C141-E230
5-7
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