The document describes the storage device hierarchy from fastest to slowest including cache, main memory, flash memory, magnetic disks, optical disks, and magnetic tapes. It then provides more details on each type of storage device including their speed, cost, size, volatility, and usage. The document also covers disk drive components and performance metrics like seek time, rotational latency, data transfer rate, and reliability measures like mean time to failure. Additional topics covered include RAID configurations, file organization methods, database storage structures, indexing techniques, and hashing.

2. Storage Device Hierarchy
Cache
Main Memory
Flash Memory
Magnetic Disk
Optical Disk
DBMS, JVP
Magnetic Tapes
Cost
Access Speed

3. •
•
•
•
•
Fastest
Most Costly Media
Small & is managed by System H/W
Generally is inbuilt on-chip memory
For storage of important & critical
instructions
• If size of cache is increased –
cost increased
benefits of cache is lost
DBMS, JVP

4. • Machine instructions are stored in main
memory
• Its is quite small for storing Database
• Its Volatile i.e. data is lost on power failure or
system crash
DBMS, JVP

5. •
•
•
•
•
EEPROM
Read is Faster
Write is very slow & complicated
4-10 microsec to write, can’t be overwritten
To overwrite, has to erase entire data of
memory
• Used generally for hand-held & digital
electronics devices
DBMS, JVP

6. • Stores the Database, data moves between Main
Memory & Disk
• Size – Few GB upto 80GB
• Size of Magnetic Disk needs increases as we
have requirement for larger capacity disks
• Can survive power failure & system crash, is
non-volatile storage media
• Disk Failure results in loss of data stored on
disk.
DBMS, JVP

7. • CD – holds about 640MB
• DVD – holds 4.7 or 8.5GB per side to 17GB for
two-sided disk
• Data is stored optically on a disk, is read by laser
• WORM-write once read many CDs & DVDs
• CD-RW & DVD-RW : For multiple writes & read
• CDs are magnetic-optical storage devices that use
optical means to read magnetically encoded data.
• DBMS, JVP archival storages
Used for

8. •
•
•
•
•
Used for Backup Storage
Cheaper & Slower Access
Sequential-access Storage
Not direct access like CDs
Used for holding large backup data of large
organization
DBMS, JVP

9. Spindle
Track i
Platter
Disk Arm
Arm Assembly
Cylinder i
DBMS, JVP
R-W Head

10. • Access Time :
Read Req. Issued – Actual Data Transfer Begin
• Seek Time : Avg. Seek Time
Time For Repositioning the arm
• Rotational Latency Time : Avg. RLT
Time waiting for sector to appear under head
• A T = S T + RL T
• Data Transfer Rate : rate of data read/write to disk
• Mean Time To Failure (MTTF)
Amount of time on avg. we expect system to work w/o
DBMS, JVP
failure, measure of reliability of disk

11. • Reliability of Disk : 1,00,000/100 = 1000 hours
• Disk Failure leads to loss of data
• So keep redundancy i.e. Mirroring of Disk
• MTTF of mirrored disk depends on MTTR, time to
replace failed disk & restore data
• First write to one copy them to other so on power
failure, blocks have complete data.
DBMS, JVP

12. • Parallel access to disks
• Improve the transfer rate by ‘Striping’
• Bit-level striping : splitting bits of each byte
across multiple disks, array of 4,8,16… disks,
increase R/W at 8 times
• Block-level striping : divide data into blocks,
each block in a disk.
• ith block is in (i mod n + 1)th disk, n=total no. of
disks in array.
• Balances load across multiple disks so access
is fast & o/p is high
DBMS, JVP

14. C
DBMS, JVP
C
C
C

15. P
DBMS, JVP
P
P

16. P
P
DBMS, JVP
P
P
P
P

17. P
DBMS, JVP
P
P
P
P
P

18. •
•
•
•
Monetary Cost of extra disk
Performance – no. of I/O Operations
Performance when Disk fails
Performance to rebuild the Data
RAID 0, 1, 5 are currently in use
DBMS, JVP

19. • File is organized logically as a sequence of
records. The records are stored in disk blocks.
Fixed Length Records
Variable Length Records
DBMS, JVP

20. • Deposit = record
acc_no:char(10);
br_nm:char(22);
bal:real;
end
Acc_n Br_nm
o
Bal
R-1
A-104 Bombay
500
R-2
A-121 Delhi
781
R-3
A-393 Pune
900
R-4
A-129 Bombay
400
R-5
A-214 Chennai 164
Total = 40 bytes
DBMS, JVP

21. Header
A-104 Bombay
500
A-121 Delhi
781
A-393 Pune
900
A-129 Bombay
400
A-214 Chennai 164
DBMS, JVP

22. • Records has varying length
• Account_list : record
Br_nm:char(22);
accounts :- array(1---infinite)
acc_no:char(10);
bal:real;
end
end
DBMS, JVP

23. • Dis. Adv. –
- Not easy to occupy space left by deleted record
Leads to small fragments on disk
- No space for records to grow
Header has info :
- No. of records
- Free space pointer
- Size of each record block
DBMS, JVP

24. • Reserved Space
• List Representation
– Anchor Block
– Over Flow Block
DBMS, JVP

25. • Heap file organization
• Sequential file organization
– Search Key
– Insert & Deleted using Overflow Block
• Hashing file organization
• Clustering file organization
DBMS, JVP

26. • A database that maintains data about
relations, stores information about the
tables of the database.
• E.g. Name of relations
Names of Attributes
Domains & Length
Constraints
DBMS, JVP

27. DBMS, JVP

28. • Ordered Indices
• Hash Indices
Aspects :- Access Type : by value or range
- Access Time
- Insertion Time
- Deletion Time
- Space Overhead
DBMS, JVP

29. • Primary Index
– Dense Index
– Sparse Index
Multilevel Indices
Secondary Indices
DBMS, JVP

30. • Hash File Organization
- Hash Function
Uniform Distribution
Random Distribution
- Bucket
Bucket Overflow & Skew
Overflow Chining
• Hash Indices
• Comparison of Indexing & Hashing
DBMS, JVP

31. DBMS, JVP