Installation guide

Software Operation Manual
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4.8.1.5 HDD Read Ahead Cache
Allow Read Ahead (Default: Enabled)—When Enabled, the drive’s read ahead cache
algorithm is used, providing maximum performance under most circumstances.
4.8.1.6 Volume Data Read Ahead
The Read data ahead parameter specifies the controller firmware algorithms which
process the Read Ahead data blocks from the disk. The Read Ahead parameter is
normal by default. To modify the value, you must set it from the command line using
the Read Ahead option. The default normal option satisfies the performance
requirements for a typical volume. The disabled value implies no read ahead. The
most efficient value for the controllers depends on your application. Aggressive read
ahead is optimal for sequential access but it degrades random access.
4.8.1.7 HDD Queue Depth
This parameter is adjusted the queue depth capacity of NCQ (SATA HDD) or Tagged
Command Queuing (SAS) which transmits multiple commands to a single target with-
out waiting for the initial command to complete..
4.8.1.8 Disk Write Cache Mode
Disk cache can be turned off to prevent data lost, turned on to increase the
performance of the machine. The following is the reason why a user might want to
turn off the cache. In case of power failure, the data stored in the disk cache waiting
to be process might be lost. The disadvantage to turn off the disk cache is that
performance will decrease dramatically.
Auto: Disk cache's setting will accord the installation of battery backup. When battery
backup is installed, Disk cache is disabled. No battery backup installed, Disk cache is
enabled.
A user can set the “Disk Write Cache Mode”: "Auto", "Enabled", or "Disabled".
4.8.1.9 Disk Capacity Truncation Mode
The RAID subsystem uses drive truncation so that drives from differing vendors are
more likely to be able to be used as spares for each other. Drive truncation slightly
decreases the usable capacity of a drive that is used in redundant units.
The controller provides three truncation modes in the system configuration: “Multiples
Of 10G”, “Multiples Of 1G”, and “Disabled”.
Multiples Of 10G: If you have 120 GB drives from different vendors; chances are
that the capacity varies slightly. For example, one drive might be 123.5 GB, and the
other 120 GB. Multiples Of 10G truncates the number under tens. This makes same
capacity for both of these drives so that one could replace the other.
Multiples Of 1G: If you have 123 GB drives from different vendors; chances are that
the capacity varies slightly. For example, one drive might be 123.5 GB, and the other
123.4 GB. Multiples Of 1G truncates the fractional part. This makes capacity for both
of these drives so that one could replace the other.