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17-1-2011 ,
/ : : (sectors): : interblock gaps (cluster) :
(Sector) (= block=page) /
(platter) (cylinder)
(track)
record : .
(values) (fields) : Byte
File :
bfr= B/R
B= bytes R= bytes
B-(bfr*R) bytes (spanned)
bfr # r
r : b : r b= r/bfr
(unspanned)
r=20.000 . :
(30 byte) (9 byte) (40 byte) (9 byte) _(8 byte) (1 byte) _(4 byte) _ (4 byte) ( 4 byte) _(3 byte)
1 -
B=512 byte =20 = 400 15
1 -
; ; ; ; R byte. bfr b,
1 - ; 20 * 512 Byte = 10kb ; : . 400
1 - 1 15 * = 30 . :
30 * 10=300 kb
1 = 400 .
300 * 400=120Mb
1 - R byte (30byte +9+40+9+8+1+4+4+4+3+1 ) R=113 bfr b,
bfr= B/R = 512/113 = 4
b=r/bfr=20000/4=5000
-
:(b/2)block - ( ) - ( ) : log2(b) block ( )
(index) () (indexing field)
block
: ( ) :
.
2 -
r = 30000 B=1024 byte R=100 byte
; 1.
2. 3.
bfr=(/R)=10 b=(r/bfr)=3000
log2b= log23000=12
2
V=9byte block P=6 byte
;
Ri=9+6=15byte bfri=1024/15=68
bfri=(/Ri)
ri
bi= (ri/bfri)= (3000/68) =45 block (log2bi) = (log245) =6 block
ri=# =3000 ( )
-
: +
3
r = 30000 B=1024 byte R=100 byte
;
bfr=(/R)=10 b= (r/bfr) =3000
b/2=3000/2=1500 .
3
- V=9byte block P=6 byte
Ri=9+6=15byte bfri= (/Ri)=1024/15=68 . O ri 30000. bi= (ri/bfri)= (30000/68)=442 block (log2bi)= (log2442)=9 block 10 block
: bfri =fo ( (fan-out))
fo>2 logfobi213 =14
!!!