Lenovo ThinkServer RD330, Software User'S Manual, Page: 45 / 401

Page 45
MegaRAID SAS Software User Guide Chapter 2: Introduction to RAID
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Configuration Planning
2.7.1.2 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 no hot spares with enough capacity to rebuild the failed
drives are available. You must insert a drive with enough storage into the subsystem
before rebuilding the failed drive.
2.8 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.
2.9 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.
2.9.1 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, 6, 10, 50, or 60.
 Does this drive group support any software system that must be available 24 hours
per day? Use RAID 1, 5, 6, 10, 50, or 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 00.
 Will this drive group contain data from an imaging system? Use RAID 0, 00, or 10.