Berkeley COMPSCI 61C - 27LecSp11RAIDx6 (9 pages)

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27LecSp11RAIDx6



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27LecSp11RAIDx6

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Lecture Notes


Pages:
9
School:
University of California, Berkeley
Course:
Compsci 61c - Machine Structures
Machine Structures Documents

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4 27 11 CS 61C Great Ideas in Computer Architecture Machine Structures Redundant Arrays of Inexpensive Disks Instructors Randy H Katz David A PaHerson hHp inst eecs Berkeley edu cs61c fa10 4 27 11 Spring 2011 Lecture 27 1 4 27 11 Spring 2011 Lecture 27 Agenda Agenda RAID Administrivia Course Summary Randy Cal Culture Dave Course EvaluaTon 4 27 11 2 Spring 2011 Lecture 27 3 RAID Administrivia Course Summary Randy Cal Culture Dave Course EvaluaTon 4 27 11 Spring 2011 Lecture 27 EvoluTon of the Disk Drive 4 Arrays of Small Disks Can smaller disks be used to close gap in performance between disks and CPUs ConvenTonal 4 disk designs 3 5 5 25 10 IBM 3390K 1986 Low End 14 High End Disk Array 1 disk design 4 27 11 IBM RAMAC 305 1956 Spring 2011 Lecture 27 Apple SCSI 1986 3 5 5 4 27 11 Spring 2011 Lecture 27 6 1 4 27 11 RAID Redundant Arrays of Inexpensive Disks Replace Small Number of Large Disks with Large Number of Small Disks 1988 Disks Capacity Volume Power Data Rate I O Rate MTTF Cost IBM 3390K 20 GBytes 97 cu e 3 KW 15 MB s 600 I Os s 250 KHrs 250K IBM 3 5 0061 320 MBytes 0 1 cu e 11 W 1 5 MB s 55 I Os s 50 KHrs 2K x70 23 GBytes 11 cu e 9X 3X 1 KW 120 MB s 8X 3900 IOs s 6X Hrs 150K Disk Arrays have potenTal for large data and I O rates high MB per cu e high MB per KW but what about reliability 4 27 11 Spring 2011 Lecture 27 7 Redundant Arrays of Inexpensive Disks RAID 1 Disk Mirroring Shadowing recovery group Each disk is fully duplicated onto its mirror Very high availability can be achieved Bandwidth sacri ce on write Logical write two physical writes Reads may be opTmized Most expensive soluTon 100 capacity overhead 4 27 11 Spring 2011 Lecture 27 9 Files are striped across mulTple disks Redundancy yields high data availability Availability service sTll provided to user even if some components failed Disks will sTll fail Contents reconstructed from data redundantly stored in the array Capacity penalty to store redundant info Bandwidth penalty to update redundant



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