Lenovo ThinkServer RD650, User Manual

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LSI Corporation
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12Gb/s MegaRAID SAS Software User Guide

March 2014
Chapter 2: Introduction to RAID
Configuration Planning
NOTE If a rebuild to a hot spare fails for any reason, the hot spare drive will be
marked as “failed.” If the source drive fails, both the source drive and
the hot spare drive will be marked as “failed.”
A cold swap requires that you power down the system before replacing a defective drive in a disk subsystem.
Rebuilding
If a drive fails in a drive group that is configured as a RAID 1, 5, 6, 10, 50, or 60 virtual drive, you can recover the lost
data by rebuilding the drive. If you have configured hot spares, the RAID controller automatically tries to use them to
rebuild failed drives. Manual rebuild is necessary if hot spares with enough capacity to rebuild the failed drives are not
available. You must insert a drive with enough storage into the subsystem before rebuilding the failed drive.
2.5 Configuration Planning
Factors to consider when planning a configuration are the number of drives the RAID controller can support, the
purpose of the drive group, and the availability of spare drives.
Each type of data stored in the disk subsystem has a different frequency of read and write activity. If you know the
data access requirements, you can more successfully determine a strategy for optimizing the disk subsystem capacity,
availability, and performance.
Servers that support video-on-demand typically read the data often, but write data infrequently. Both the read and
write operations tend to be long. Data stored on a general-purpose file server involves relatively short read and write
operations with relatively small files.
2.6 Number of Drives
Your configuration planning for the SAS RAID controller depends in part on the number of drives that you want to use
in a RAID drive group.
The number of drives in a drive group determines the RAID levels that can be supported. Only one RAID level can be
assigned to each virtual drive.
Drive Group Purpose
Important factors to consider when creating RAID drive groups include availability, performance, and capacity. Define
the major purpose of the drive group by answering questions related to these factors, such as the following, which are
followed by suggested RAID levels for each situation:

Will this drive group increase the system storage capacity for general-purpose file and print servers? Use RAID 5,
RAID 6, RAID 10, RAID 50, or RAID 60.

Does this drive group support any software system that must be available 24 hours per day? Use RAID 1, RAID 5,
RAID 6, RAID 10, RAID 50, or RAID 60.

Will the information stored in this drive group contain large audio or video files that must be available on
demand? Use RAID 0 or RAID 00.

Will this drive group contain data from an imaging system? Use RAID 0, RAID 00, or RAID 10.
Fill out the following table to help you plan the drive group configuration. Rank the requirements for your drive group,
such as storage space and data redundancy, in order of importance, and then review the suggested RAID levels.