COSI 127b Introduction to Database Systems by x6eVhef

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									CMSC424: Database Design


      Data Storage
Storage Hierarchy
             Storage Hierarchy
• Cache - Super fast; volatile
• Main memory - 10s or 100s of ns; volatile
• Flash memory - limited number of write/erase cycles;
  non-volatile, slower than main memory
   – Intel announcement

• Magnetic Disk - Non-volatile
• Optical Storage - CDs/DVDs; Jukeboxes
• Tape storage - Backups; super-cheap; painful to access
 Jim Gray’s Storage Latency Analogy:
     How Far Away is the Data?

             Andromeda
10 9   Tape /Optical                    2,000 Years
        Robot


 10 6 Disk               Pluto              2 Years




                         Sacramento          1.5 hr
100    Memory
 10    On Board Cache     This Hotel         10 min
  2    On Chip Cache       This Room
  1    Registers                     My Head  1 min
1956
IBM RAMAC
24” platters
100,000 characters each
5 million characters
1979
SEAGATE
5MB
1998
SEAGATE
47GB
2004
Hitachi
400GB
Height (mm): 25.4. Width (mm): 101.6. Depth (mm): 146. Weight (max. g): 700
2006
Western Digital
500GB
Weight (max. g): 600g
“Typical” Values
     Diameter:      1 inch  15 inches
     Cylinders:     100  2000
     Surfaces:      1 or 2
     (Tracks/cyl)   2 (floppies)  30
     Sector Size:   512B  50K
     Capacity:      360 KB (old floppy)
                     300 GB
Reliability Issues:
  Mean time to failure (MTTF):
     57 to 136 years
  Given 1000 new disks with 1,200,000
  hours of MTTF, on average one of them
  will fail in 1200 hours = 50 days.

								
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