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Disks; Distributed Systems
Tanenbaum ch. 5.4 Distributed Systems Tanenbaum ch. 8.3
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Disk Hardware Information written onto the disk in concentric circles
At any arm position,each head can read a track All the tracks for a given arm position forms a cylinder
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Disk Parameters For the 20GB disk, 281 x 512=140KB/track
Transfer a track in 1 rotation time of 8.33ms or a transfer rate of 17 MB/sec 7200rpm
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Disk Geometry Virtual Physical Divide the disk into zones with more sectors on the outer zones than the inner zones
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Strips and Stripes
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RAID Use parallel I/O to improve performance
Redundant Array of Inexpensive Disks Organized into 6 levels stripe
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RAID Levels Level 3-5
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Nested RAID Combine data redundancy and performance
of Raid 0 and Raid 1 Raid 1+0 is better for recovery
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Comparisons of Multiple CPU Systems
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Distributed Systems Multiple complete computers connected by a network
Example: our site: blade01, …, blade42, ulab,… are all separate computer systems, but networked together sharing a global distributed NFS file system login onto blade12, look at your login dir login onto ulab, see the same files Distributed system turns a loosely connected bunch of machines into a coherent system
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Middleware
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Networking Hardware
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Networking Services
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Network Protocols Protocol- the set of rules by which computers communicate Organize as a stack OSI Layer Example Kind of software (UNIX, Windows) Application Web server, browser User-level Transport TCP Kernel Network IP Kernel Data Link Ethernet Kernel Physical Cat5 cable, etc. Hardware
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Interaction of Protocols
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