The advantages of RAID modes supported
Fault tolerance and performance are important terms to understand when choosing a RAID mode.
Fault tolerance
Fault tolerance is the ability of a RAID array to withstand and recover from a drive failure. Fault
tolerance is provided by redundancy. Therefore, RAID 0 has no fault tolerance because it does not
copy data to another HDD. With RAID 1 and Recovery, one drive can fail without causing the array to
fail. With Recovery, however, the restoration of a single file or an entire HDD is much simpler than
with RAID 1 alone. With RAID 5, one of the three HDDs can fail without causing the array to fail.
Performance
Performance is easy to understand, but it is difficult to measure because it involves several factors,
some of which are beyond the scope of this document. Overall storage performance is determined by
write performance and read performance, both of which vary based on the RAID technology selected.
●
RAID 0 (striping) improves overall storage performance because data can be written and read
simultaneously across two HDDs.
●
Recovery and RAID 1 (mirroring) writes the same data to both HDDs; therefore, write
performance may be slower. However, data can be read from both HDDs, so the read
performance can be higher than that of a single non-RAID HDD.
● RAID 5 performs at a level between RAID 0 and RAID 1.
6 Chapter 2 RAID technology overview
