Dell PowerEdge RAID Controller S110 - Manual (Page 59)

Appendix B 57
1
Appendix B
About RAID
A RAID disk array is a group of independent physical disks that provide high
performance by increasing the number of drives used for saving and accessing
data. A RAID disk subsystem improves I/O performance and data availability.
The physical disks appear to the host system either as a single storage unit or
multiple logical units. Data throughput improves because several disks are
accessed simultaneously. RAID systems also improve data storage availability
and fault tolerance. Data loss caused by a physical disk failure can be
recovered by rebuilding missing data from the remaining physical disks
containing data or parity.
NOTE: When a physical disk in a RAID 0 virtual disk fails, data is lost because there
is no redundancy for this RAID level. However, when a physical disk in a
RAID 1, RAID 5, or RAID 10 fails, data is preserved because there is redundancy
with these RAID levels.
RAID Levels and Characteristics
Volume (can be created only using the PERC S110 BIOS Configuration
Utility. Dell OpenManage Server Administrator Storage Management can
manage a Volume but cannot create it.)
A virtual disk type that links available space on a single physical disk and
forms a single logical volume on which data is stored.
• Concatenation allows access to a single physical disk.
• Concatenation does not provide performance benefits or data redundancy.
• When a physical disk in a concatenated virtual disk fails, data is lost from
that virtual disk. Because there is no redundancy, data can be restored only
from a backup.
Understanding RAID Levels
A PERC S110 adapter supports the following RAID levels:
A5_bk0.book Page 57 Thursday, May 29, 2014 11:37 AM