Areca 24/4 Internal/External Port Pcie 3.0 12 Gb/s SAS/SATA Raid Controller 2Gb Cache - Manual (Page 180)

WEB BROWSER-BASED CONFIGURATION
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• JBOD/RAID Configuration
JBOD is an acronym for “Just a Bunch Of Disk”. A group of
hard disks in a RAID box are not set up as any type of RAID
configuration. All drives are available to the operating system
as an individual disk. JBOD does not provide data redundancy.
User needs to delete the RAID set, when you want to change
the option from the RAID to the JBOD function.
• SATA NCQ Support
The controller supports both SAS and SATA disk drives. The
SATA NCQ allows multiple commands to be outstanding within
a drive at the same time. Drives that support NCQ have an
internal queue where outstanding commands can be dynami-
cally rescheduled or re-ordered, along with the necessary
tracking mechanisms for outstanding and completed portions
of the workload. The SAS RAID controller allows the user to
select the SATA NCQ support: “Enabled” or “Disabled”.
• 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.
• Volume Data Read Ahead
The volume read data ahead parameter specifies the control-
ler 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 com-
mand line using the Read Ahead option. The 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. Aggres-
sive read ahead is optimal for sequential access but it
degrades random access.
• HDD Queue Depth
This parameter is adjusted the queue depth capacity of NCQ
(SATA HDD) or Tagged Command Queuing (SAS HDD) which
transmits multiple commands to a single target without
waiting for the initial command to complete.