Re: which PC

rfischer@xxxxxxxxx (Ray Fischer) wrote:
Floyd L. Davidson <floyd@xxxxxxxxxx> wrote:
"dennis@home" <dennis@xxxxxxxxxxxxxxxxxxxxxx> wrote:
"Floyd L. Davidson" <floyd@xxxxxxxxxx> wrote:

I would have to agree at least in part.. you don't need to defrag a disk
(note disk not file system as a file system may not be on a disk).
You don't even have to defrag windows.

However there /is/ a performance boost from defraging a file system.

Only if you have a very poorly designed filesystem.
*Very* poorly designed.

How many file systems have you designed?

Cute, but irrelevant. (The answer however is greater
than zero, and certainly higher than the number you have
designed.)

Yep, you don't understand filesystems. (Or harddisks
either!)

Given your other posts in this thread, you're hardly one to
criticize.

Cute again, but cannot demonstrate it to be true...

The only systems where this isn't true are specialised ones like some
databases use and even then the database will have some sort of optimisation
built in.

There is no need for defragmentation on any of the
modern filesystems that have been designed for unix
based systems.

Why not?

For basically three reasons.

First, there are fragmented i/o requests, which if
nothing else had changed would have the exact same
effect on performance as fragmented disk files. On a
single user single tasking system (say, CP/M, MSDOS, or
early Windows versions) sequential file i/o was not
fragmented, and hence non-fragmented file i/o was faster
than fragmented file i/o. But with multi-user,
multi-tasking, multi-threaded, multi-processor systems
the requests themselves are necessarily going to be
fragmented, and therefore it makes little difference
whether the disk is fragmented or not (it might even be
faster if it is!).

Beyond that, hard disk technology has advanced to avoid
many of the inherent problems with fragmentation.
Instead of physical i/o being done in the order the
requests are received, the data is buffered, and the i/o
requests are then ordered for optimum speed (eliminating
duplicate cylinder reads and avoiding excessive seek
operations).

Last but not least, modern OS's have two features that
reduce the effects of disk fragmentation. Disk i/o is
buffered, which can often completely eliminate any
physical disk i/o at all (reads are eliminated, writes
can be delayed). The filesystems accomplish other
optimizations too, by grouping data together in
different sized chunks (fewer fragments) and then
optimizing placement of tail fragments to allow them be
on the same cylinder as other fragments in order to
avoid seek operations.

As I originally said, defragmentation is not required
on anything but a very poorly designed system.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.

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