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You can configure the VB-B8283JDGG storage
appliance to use any of the following storage policies to map the
appliance’s physical hard drives to virtual drives that are visible
to the host computer. The virtual drives are called volumes. The
host operating system treats each volume as if it were a single
physical drive. This virtualization allows you to overcome
restrictions that are imposed by physical hard drives, such as
speed, storage capacity or data storage reliability.
CLEAN MODE
The CLEAN MODE storage policy
enables each hard drive to be seen separately as one drive. When
using a SATA host controller, CLEAN MODE should only be used if the
SATA host controller provides Port Multiplier (PM) support. If a
host is not PM-aware, only a single drive is presented (drive 1). No
such limitation if using a USB host connection.
The CLEAN MODE storage policy is available for a standalone
(non-cascaded) storage or the top-level node of a cascaded
configuration, but not for subordinate nodes. Even though you can
use the MODE SWITCH to select CLEAN MODE for any node in a cascaded
configuration, only the first CLEAN MODE volume of any subordinate
node is detected by your host. Therefore, selecting CLEAN MODE for
any subordinate node is not recommended.
In a CLEAN MODE configuration, the VB-B8283JDGG storage
appliance directly exposes each physical drive.
The CLEAN MODE will not clean up the drives partition if the drives
were use as single drive before.
LARGE MODE
The LARGE MODE storage policy concatenates a series of physical hard
drives as a single large volume; resulting in a seamless expansion
of virtual volumes beyond the physical limitations of singularly
connected hard drives. VB-B8283JDGG storage policy delivers maximum
storage space without a single large capacity and costly hard drive.
Any node within a cascaded configuration can be set to LARGE MODE.
Hard drives 1 to 8 are concatenated into a single virtual volume in
the Figure below with a storage capacity that is equal to the sum of
each of the physical hard drives 1 to 8.
It is also possible to create a LARGE volume
using only a single hard disk drive connected to Port 1. However, it
is not possible to expand an existing LARGE volume by adding another
hard disk drive and still preserve any existing data on that volume.
R00 MODE
The R00 MODE storage policy distributes access across all hard disks
by three RAID systems. R00 MODE presents the best data speed but no
data redundancy. R00 MODE storage policy accelerates hard disk drive
operating speed by using many disks in parallel. Hard disk drive
data segments are written to different disks simultaneously which
increases performance while sacrificing data redundancy.
To implement the R00 MODE storage policy, the VB-B8283JDGG Storage first creates 2 single virtual volumes that are striped
across hard drive(s) on SYS1 and SYS2 individually, and then striped
across both virtual volumes again.
It is also possible to create a R00 volume using
only a single hard disk drive connected to Port 1. However, the
VB-B8283JDGG storage appliance directly exposes 1 physical drive,
and it will clean up the drives partition even if the drives were
use as single drive before.
R30 MODE
The R30 MODE adds fault tolerance to drive striping by including
parity information with the data. R30 MODE dedicates the equivalent
of two drives for storing parity stripes on both systems (SYS1 and
SYS2), and then stripe the systems together. The data and parity
information are arranged on the drive arrays so that paritys are
written to two drives on both systems (SYS1 and SYS2). The following
example illustrates how the parity is rotated from drive to drive.
The R30 MODE uses less capacity for protection
and is the preferred method to reduce the cost per megabyte for
larger installations.
In exchange for low overhead necessary to implement protection, the
R30 MODE degrades performance for all write operations. The parity
calculations for R30 MODE may result in read performance that is
somewhat slower than the write performance.
The resulting storage capacity of the virtual R30 volume will be N-2
times (“N” is the number of drive) of the smallest drive.
If one drive fails, the virtual R30 volume is
still usable, but it is in a vulnerable state because its mirrored
hard drive is inaccessible. When the offline drive comes back
online, the appliance begins a rebuild process immediately to
restore data redundancy. A message appears in the LED indicator to
notify you that a rebuild is in progress.
Although the volume remains available during the rebuild process,
the volume is susceptible to data loss through damage to the
remaining drive until redundancy is restored at the end of the
rebuild and verification process. Host access takes precedence over
the rebuild process. If you continue to use the virtual R30 volume
during the rebuild, the rebuild process will take a longer time to
complete, and the host data transfer performance will also be
affected.
It is also possible to create a R30 volume using only a single hard
disk drive connected to Port 1. However, the VB-B8283JDGG storage
appliance directly exposes 1 physical drive, and it will clean up
the drives partition even if the drives were use as single drive
before.
R50 MODE
The R50 MODE adds fault tolerance to drive striping by including
parity information with the data. R50 MODE dedicates the equivalent
of one drive for storing parity stripes on both systems (SYS1 and
SYS2), and then stripe the systems together. The data and parity
information is arranged on the drive array so that parity is written
to all drives on both systems (SYS1 and SYS2). The following example
illustrates how the parity is rotated from drive to drive.
The R50 MODE uses less capacity for protection
and is the preferred method to reduce the cost per megabyte for
larger installations.
In exchange for low overhead necessary to implement protection, the
R50 MODE degrades performance for all write operations. The parity
calculations for R50 MODE may result in read performance that is
somewhat slower than the write performance.
The resulting storage capacity of the virtual R50 volume will be N-2
times (“N” is the number of drive) of the smallest drive.
If one drive fails, the virtual R50 volume is
still usable, but it is in a vulnerable state because its mirrored
hard drive is inaccessible. When the offline drive comes back
online, the appliance begins a rebuild process immediately to
restore data redundancy. A message appears in the LED indicator to
notify you that a rebuild is in progress.
Although the volume remains available during the rebuild process,
the volume is susceptible to data loss through damage to the
remaining drive until redundancy is restored at the end of the
rebuild and verification process. Host access takes precedence over
the rebuild process. If you continue to use the virtual R50 volume
during the rebuild, the rebuild process will take a longer time to
complete, and the host data transfer performance will also be
affected.
It is also possible to create a R50 volume using only a single hard
disk drive connected to Port 1. However, the VB-B8283JDGG storage
appliance directly exposes 1 physical drive, and it will clean up
the drives partition if the drives were use as single drive before.
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