Re: Why ext3 doesn't need defragmentation ?
hi ya
> David Brodbeck wrote:
>
> On Nov 30, 2007, at 9:45 AM, Stefan Monnier wrote:
> > No. The NTFS file system does not need defragmentation.
all file systems can use a defragmentor
lets assume a disk format of:
1 2 3 4 5 6 7 8 9 10 ...... 63 ( aka sectors )
if you try to read/write a file starting sector 1 into your disk buffer,
you may or may not have disk buffer space left to read another 512Byte
from sector 2...
if you wait a bit, few milliseconds for the system to services its
disk interrupts, you now have disk buffer space to read sector 2 ..
but since you waited too long, sector 2 came and went, so now you have
to wait for a whole revolution before you can read sector 2
----
if you format using, than you may or may not have time to read sector 2
1 11 21 31 41 51 61 2 12 22 32 42 52 62 3 13 23 33 43 53 63 4 14...
the defragmentor can be used to move sectors around to optimize
reading the whole file w/o waiting for the next revolution
- how the defragmentor displays used and unused sectors
can make a big difference in the pretty pic you see vs the
actual performance
what you see the defragmentor showing would be a continuously
allocated file instead of scattered across various sectors
within a track or having to move the heads to a different tract
to get to the next 512byte
there's only 512bytes per sector
63 sectors per track
and any number of cylinders depending on your disk size
the number of heads and disk buffer size would depend on your
disk drive manufacturer and model#
one traack is 512MB * 62 == 31.744KBytes
with 16 physical heads .... you can read 509.904KBytes per revolution
all un-used disk sectors belonging to a different file is read and
discarded ... what a waste
with 8MB or 16MB disk buffer .. you can read lots of tracks before
the disk buffer is full ... there should NOT be a "slow" system
lba ...
maps all the cylinder/heads/sector into other whacky numbers ( lba blocks )
c ya
alvin
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