User`s guide

2
BT-3045 storage policies
The BT-3045 Data Marshalling System provides the following storage policies, for mapping physical
to virtual drives. You can use the Basic Configuration Wizard or the Advanced Configuration Wizard
to choose from these policies. It is important to choose an adequate policy to make the best use of
your Storage Appliance.
This storage policy grants the host computer direct access to a physical disk
drive. With JBOD (just a bunch of disks), the number of available virtual drives is
equal to the number of physical drives. JBOD is also called the bypass mode
because the host bypasses the virtualization engine to access the drive directly.
JBOD
This storage policy makes all data stored in duplicate on separate hard disk drives
to prevent data loss due to drive failure. At least two hard disk drives mirror each
other at all times, equivalent to RAID 1. Every write operation goes to both drives.
SAFE provides the highest level of data protection, but halves the amount of
storage space because all data must be stored twice.
SAFE
To implement the SAFE storage policy, the Basic Configuration Wizard creates
two volumes. Each volume consists of two hard disk drives that mirror each other.
The remaining hard disk drive is specified as a Hot Spare for both volumes.
This storage policy makes multiple physical hard disk drives strung together
(concatenated) and treated as one large volume. This configuration allows you to
increase logical volume size beyond the capacity of individual hard disk drives.
BIG provides the maximum amount of storage space, but no additional
performance of data redundancy.
BIG
The Basic Configuration Wizard implements the BIG storage policy by
concatenating all the hard disk drives into a single volume.
In FAST storage policy, the I/O processing is balanced evenly to all drives in a
method known as striping, equivalent to RAID 0. Striping increases storage
operation speed by using several disk drives in parallel. Each portion of data is
divided into segments that are written to different disks simultaneously. Striping
provides improved performance but does not enhance reliability because there is
no way to retrieve or reconstruct data stored on a failed drive.
FAST
To implement the FAST storage policy, the Basic Configuration Wizard creates a
single volume of four hard disk drives in a striped format. The remaining hard disk
drive is designated as a standalone volume using the BIG storage policy.
FAFE and BIG
A storage policy in which one-half of the available storage space is concatenated.
The other half mirrors the first half to provide full data redundancy.
In the SAFE and BIG storage policy, the Basic Configuration Wizard mirrors the
concatenated disks to create a volume consisting of four disk drives and
designates the remaining hard disk drive as a Hot Spare
A storage policy in which an array of stripes is created. Each strip consists of two
mirrored drives. SAFE and FAST provide the I/O load balancing features of
striping and the added reliability of mirrored data, equivalent to RAID 1+0. Data are
written to mirrored disks in a striped format.
FAFE and FAST
In the SAFE and FAST storage policy, data are written to mirrored disks in astriped
format. The Basic Configuration Wizard creates a virtual drive consisting of four
hard disk drives and designates the remaining drive as a Hot Spare