AMCC 3WARE 720-0138-00, Руководство по установке

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Configuring Units
28 3ware 9000 Series Serial ATA RAID Controller Installation Guide
Note:
You must attach drives before you can configure
RAID arrays. If no drives are attached to the 3ware
RAID controller, the 3ware BIOS will not be installed.
Understanding RAID Concepts and
Levels
The following concepts are important to understand when selecting
the appropriate RAID level for a system:
„
Arrays and Units
. In the storage industry, the term “array” is
used to describe two or more disk drives that appear to the
operating system as a single unit. When you work with 3ware
software, “unit” is the term used to refer to an array of disks
that is configured and managed through the 3ware software.
Single-disk units can also be configured in the 3ware software.
„
Mirroring
. Mirrored arrays write data to paired drives
simultaneously. If one drive fails, the data is preserved on the
paired drive. Mirroring provides data protection through
redundancy. In addition, mirroring using a 3ware RAID
controller provides improved performance because 3ware’s
TwinStor technology reads from both drives simultaneously.
„
Striping
. Striping across disks allows data to be written and
accessed on more than one drive, at the same time. Striping
combines each drive’s capacity into one large volume. Striped
disk arrays achieve highest transfer rates and performance at
the expense of fault tolerance.
„
Distributed Parity
. Parity works in combination with striping
on RAID 5 and RAID 50. Parity information is written to each
of the striped drives, in rotation. Should a failure occur, the data
on the failed drive can be reconstructed from the data on the
other drives.
„
Hot Spare
. A single drive that is not used for user data, but
rather as an extra drive that is online and available to