Mass Storage and I/O - II RAID: Redundant Array of Inexpensive Disks - PDF document

CSC 4103 - Operating Systems RAID Structure Spring 2008 • As disks get cheaper, adding multiple disks to the same system provides increased storage space, as well as Lecture - XIX increased reliability and performance. 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 10 th , 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"*.) � "-&+$/*+9*$"&$'%&/$&#1%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%#)$0)12+14"*.)=> 7 8 RAID Level 2 RAID Level 2 � 8&)&$)11+1$.+11).#%*5$"-5+1%#64$#6"#$ )40-+7&$'%&/?&#1%0%*5$&#1"#)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 10 RAID Level 3 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;$,8#$%#$)40-+7&$ &#1%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 14 RAID Level 5 RAID Level 5 � /*+9*$"&$&#1%0%*5$9%#6$0"1%#7 � #6)$4+&#$0+08-"1$B:C!$-)()- � &%4%-"1$#+$-)()-$G$%*$#6"#$%#$&#1%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 • Similar to RAID 5, but uses dual distributed parity hierarchy beyond primary memory and secondary • more reliability versus less data space storage to incorporate tertiary storage — usually implemented as a jukebox of tapes or removable disks. • Usually incorporate tertiary storage by extending the file system. – 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