Raid Overview - Spectra Logic Spectra RXT350 User Manual

RAID Overview

RXT media packs support RAID, which stands for Redundant Array of Independent
Disks. It is a system of using multiple hard drives for sharing or replicating data. RAID
is not a replacement for a good backup system and policy; rather, it should be seen as
added insurance against data loss and business disruption. Your RXT media arrives set
with the RAID level you specified on ordering the RXT media pack.
RXT Media RAID Level Options
There are multiple RAID levels, each one providing different levels of performance and
protection. RXT media is available in four RAID configurations:
• RAID 0 provides the best read/write performance and takes full advantage of
available capacity, but provides no redundancy. Data is split up across the drives
(called striping) to maximize throughput. However, if a disk fails, your data is
unrecoverable.
• RAID 1 offers moderate performance and full redundancy. Data is mirrored to—that
is, exact copies are written to—two different disks. If one disk fails, the remaining
one has a complete version of your data, and that data can be replicated once the
bad drive is replaced. However, this option halves available disk capacity. For
example, 1 TB of raw disk provides 500 GB of usable capacity in a RAID 1
configuration.
• RAID 5 provides good performance with a reasonable amount of data protection.
Data is striped across multiple drives, and error correction information—parity—
distributed among the drives. If one drive fails, the parity information from the
remaining disks can be used to rebuild your data. The penalty of redundancy in this
configuration is that parity consumes approximately 20% of your total disk capacity.
• RAID 1+0 (RAID 10) is a combination of RAID 1 and RAID 0; it provides increased
performance over RAID 1. Data is first mirrored to two different disks, then that
mirrored data is striped across multiple disks.
Choosing the RXT Media RAID Level
Choose a RAID level based on your risk tolerance as well as your capacity and
performance needs.
• RAID 0 provides the best performance, but no redundancy; a single disk drive
failure results in data loss.
• RAID 1 provides redundancy, but slower performance. If a primary or mirrored
drive fails, data is still available on the alternate drive. When the failed drive is
replaced, data is replicated (i.e. mirrored) to that drive to ensure full redundancy.
• RAID 5 and 1+0 can be viewed as midrange options for both performance and
protection.
Chapter 7. Best Practices for RXT
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