19 Mass Storage Io Ii

CSC 4103 - Operating Systems Spring 2008

RAID Structure • As disks get cheaper, adding multiple disks to the same system provides increased storage space, as well as increased reliability and performance.

Lecture - XIX

Mass Storage and I/O - II

• RAID: Redundant Array of Inexpensive Disks – multiple disk drives provides reliability via redundancy.

• RAID is arranged into six different levels.

Tevfik Ko!ar Louisiana State University April 10th, 2008

1

RAID Levels

RAID (cont) • RAID schemes improve performance and improve the reliability of the storage system by storing redundant data. – Mirroring (shadowing): duplicate each disk • Simplest but most expensive approach

– Block interleaved parity uses much less redundancy. – Data Striping: splitting each bit (or block) of a file across multiple disks.

RAID Level 0

RAID Level 0

!"#"$%&$'%(%')'$%*#+$,-+./&$"*'$%&$ &01)"'$%*$"$2%3)'$+1')1$"4+*5$"--$#6)$ '%&/&$%*$#6)$"11"7 ! '+)&$*+#$01+(%')$"*7$2"8-#$#+-)1"*.) ! "-&+$/*+9*$"&$'%&/$
%0%*5 ! %401+()&$1)"'$"*'$91%#)$0)12+14"*.)$ (%"$0"1"--)-$"..)&& !

5

6

RAID Level 1

RAID Level 1

!

:--$'"#"$91%##)*$#+$#6)$01%4"17$'%&/$%&$ 91%##)*$#+$#6)$4%11+1$'%&/

!

01+(%')&$"$1)'8*'"*#;$%')*#%."-$.+07$+2$"--$ '"#"

!

01+(%')&$2"8-#$#+-)1"*.)

!

"-&+$/*+9*$"&$'%&/$4%11+1%*5$

!

"-&+$5)*)1"--7$%401+()&$1)"'$0)12+14"*.)$ <,8#$4"7$')51"')$91%#)$0)12+14"*.)=> 7

RAID Level 2

8

RAID Level 2

!

8&)&$)11+1$.+11).#%*5$"-5+1%#64$#6"#$ )40-+7&$'%&/?
%0%*5$
"#)57$#6"#$,1)"/&$ "$2%-)$%*#+$,7#)&$"*'$&01)"'&$%#$".1+&&$ 48-#%0-)$'%&/&

!

@6)$)11+1?.+11).#%+*$4)#6+'$1)A8%1)&$ &)()1"-$'%&/&

!

01+(%')&$2"8-#$#+-)1"*.)

!

,8#$%&$*+#$"&$)22%.%)*#$"&$+#6)1$B:C!$-)()-&$ 9

RAID Level 3

10

RAID Level 3

!

&%4%-"1$#+$B:C!$-)()-$D;$,8#$%#$1)A8%1)&$+*-7$ +*)$'%&/$2+1$0"1%#7$'"#"

!

&822)1&$21+4$"$91%#)$,+##-)*)./;$,)."8&)$"--$ 0"1%#7$'"#"$%&$91%##)*$#+$"$&%*5-)$'1%()

!

,8#$01+(%')&$&+4)$1)"'$"*'$91%#)$ 0)12+14"*.)$%401+()4)*#>$

11

12

RAID Level 4 !

!

!

RAID Level 4

&%4%-"1$#+$B:C!$-)()-$E;$,8#$%#$)40-+7&$
%0)'$'"#"$%*$48.6$-"15)1$,-+./&$+1$ &)54)*#& *+#$"&$)22%.%)*#$"&$B:C!$-)()-$F;$,)."8&)$ <"&$%*$B:C!$-)()-$E=$"--$0"1%#7$'"#"$%&$ 91%##)*$#+$"$&%*5-)$'1%() &+$B:C!$-)()-$G$&822)1&$21+4$"$91%#)$ ,+##-)*)./$"*'$%&$*+#$5)*)1"--7$8&)'>$ 13

RAID Level 5 ! ! !

!

!

!

14

RAID Level 5

/*+9*$"&$
%0%*5$9%#6$0"1%#7 #6)$4+&#$0+08-"1$B:C!$-)()&%4%-"1$#+$-)()-$G$%*$#6"#$%#$
%0)&$#6)$'"#"$%*$-"15)$ ,-+./&$".1+&&$"--$#6)$'%&/&$%*$#6)$"11"7 C#$'%22)1&$%*$#6"#$%#$91%#)&$#6)$0"1%#7$".1+&&$"--$#6)$ '%&/& @6)$'"#"$1)'8*'"*.7$%&$01+(%')'$,7$#6)$0"1%#7$ %*2+14"#%+* @6)$'"#"$"*'$0"1%#7$%*2+14"#%+*$"1)$"11"*5)'$+*$ #6)$'%&/$"11"7$&+$#6"#$#6)$#9+$"1)$"-9"7&$+*$ '%22)1)*#$'%&/& 15

16

Hierarchical Storage Management (HSM)

RAID Level 6

• A hierarchical storage system extends the storage hierarchy beyond primary memory and secondary storage to incorporate tertiary storage — usually implemented as a jukebox of tapes or removable disks. • Usually incorporate tertiary storage by extending the file system.

• Similar to RAID 5, but uses dual distributed parity • more reliability versus less data space

– Small and frequently used files remain on disk. – Large, old, inactive files are archived to the jukebox.

• HSM is usually found in supercomputing centers and other large installations that have enormous volumes of data.

17

Hierarchical Storage Management