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Ns 10 ms 1s 1hr each level acts as a cache of lower

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Unformatted text preview: Technology is amazing   Flying a 747 6” above the ground   Reading/wriKng a strip of postage stamps   But …   Jets do crash … 31 May 2012 Disks and File Systems 6 University of Washington Memory hierarchy 100 bytes CPU registers 32KB L1 cache 256KB 1GB 1TB Primary Memory 1 ns 4 ns 60 ns Secondary Storage Tertiary Storage 1PB   31 May 2012 L2 cache < 1 ns 10 ms 1s-1hr Each level acts as a cache of lower levels Disks and File Systems 7 University of Washington Memory hierarchy: distance analogy seconds 1 minute 10 minutes 1.5 hours 2 years 2,000 years CPU registers L1 cache L2 cache Primary Memory Secondary Storage “My head” “This room” “This building” Olympia Pluto Tertiary Storage Andromeda 31 May 2012 Disks and File Systems 8 University of Washington © 2004 Jim Gray, Microsoft Corporation 31 May 2012 Disks and File Systems 9 University of Washington Disks and the OS   Disks are messy, messy devices   errors, bad blocks, missed seeks, etc.   Job of OS is to hide this mess from higher ­level so_ware (disk hardware increasingly helps with this)   low ­level device drivers (iniKate a disk read, etc.)   higher ­level abstracKons (files, databases, etc.)   (modern disk drives do some of this masking for the OS)   OS may provide different levels of disk a...
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