StorCase Technology InfoStation 5-Bay SATA 3Gbps RAID - Manual (Page 31)

InfoStation 5-Bay RAID User's Guide - Rev. C00 StorCase Technology, Inc.
RAID Configuration 21
RAID BASICS
NOTES: The configuration and use of RAID requires a certain level of expertise and
experience on the part of the user/integrator. Since there are many configur-
ation options and variables (i.e.. host platforms, applications, etc.), only general
guidelines will be discussed in this User's Guide.
Also refer to the disk manufacturer's documentation for specific information
regarding the disks.
RAID (Redundant Array of Independent Disks) technology manages multiple disk drives to
enhance I/O performance and provide redundancy (in order to withstand any failure of in-
dividual drives, without loss of data). There are different RAID levels, each having their own
advantages and disadvantages.
RAID 0 (Striped Disks)
In a RAID 0 array, data is distributed (also known as striped) across the disks in the array.
The array appears to the server as one large disk with a capacity approximately equal to the
combined capacity of the physical disks. Because multiple reads and writes can be handled
in parallel, the input/output performance of the array is much better than that of a single physical
disk.
RAID 0 arrays do not store redundant data, so they are not true RAID applications. If one disk
fails, the entire array fails and all array data is lost. The fault-tolerance of a RAID 0 is less than
that of any single disk in the array. The term RAID 0 is widely used for these arrays however,
because they are conceptually similar to true RAID applications.
RAID 1, 0/1, and 10 (Mirrored Disks)
In RAID 1, RAID 0/1, and RAID 10 arrays (commonly referred to as mirrored arrays), disks are
paired, with both disks in the pair containing the same data. When data is written to a mirrored
array, it is written twice - once to each disk in the pair. A RAID 1 array has only one set of
paired disks. A RAID 10 array has multiple pairs, across which data is striped.
The read performance of RAID 1 arrays can be much greater than that of a single disk, while
the write performance is slightly lower. In RAID 1/10 arrays, both read performance and write
performance are better than those of a single disk.
JBOD
JBOD (Just a Bunch Of Disks) is a virtual disk that can either be an entire disk drive or just a
segment of a single disk drive.