http://www.zeropage.de
zeropage is © by the L13-Crew, all part of TUI-NET

RAID: Redundant Array of Inexpensive Disks


terms

ECCError Correction Code
member diska disk drive that is part of an array
mirrorduplicate data :-)
stripedata-distribution over the disks of an array
stripe sizesize of one elementary addressable data block of an array
strip sizesize of the part of one stripe which resides on a single disk (in contrast to the whole array)
rankthe group of member disks that are related to a logical drive

RAID levels

RAID level# of diskscapacity (netto)capacity "lost"description
single disk1c0no redundancy and no speed-up
JBOD
Just a Bunch Of Disks
nn * c0disks are simply concatenated; may even be of different sizes
RAID level 0
block striping
mm * c0at least 2 disks, no redundancy, simply making a virtual large disk out of all member disks. May result in higher I/O-performance if block striping instead of the (older) spanning-only method is used (see JBOD above therefore)
RAID level 1
drive mirroring or duplexing
n + rn * cr * cat least 2 disks, all data is written to both disks, may improve read-performance and may degrade write-performance. Can be used in combination with multiple controllers (typically called duplexing)
RAID level 2
striping with ECC
n + rn * cr * cdata is distributed in single bits over the member disks, with ECC
RAID level 3
byte striping with parity
n + 1 (n ≥ 2)n * ccparity information is stored on a dedicated disk
RAID level 4
block striping with parity drive
n + 1 (n ≥ 2)n * cclike RAID level 3, but not on block level instead of byte level
RAID level 5
block striping with distributed parity
n + 1 (n ≥ 2)n * cclike RAID level 4, but parity is distributed over all disks
RAID level 6
block striping with 2 distributed parities
n + 2 (n ≥ 2)n * c2 * clike RAID level 5, but with redundant parity information
RAID level 7.p
block striping with p distributed parities
n + p (n ≥ 2)n * cp * clike RAID level 6, but with (n-1)'th redundancy of parity information
RAID level 0+1
mirrored stripeset
m * 2m * cm * c
RAID level 10
striped mirrors
2 * (n + r)2 * n * c2 * r * c
RAID level 50
striped distributed parity
2 * (n + 1) (n ≥ 2)2 * n * c2 * c
RAID level 51
mirrored distributed parity
2 * (n + 1) (n ≥ 2)n * c(n + 1) * c
RAID level 60
striped distributed double parity
2 * (n + 2) (n ≥ 2)2 * n * c4 * c
NRAID
tbdtbdtbdtbd