Off topic I suppose but should put your mind at rest. I apologise
in advance if I'm teaching Granny about egg sucking...
In most cases stopping and restarting a defrag should have no
adverse effect
on the system. The purpose of defrag. is to store files without
them being
scattered in small blocks or fragments of data across the disk, and
preferably files that would be used together, stored together. The idea
being the less the drive heads have to move to read the data, the
quicker
the read from disk.
However, when we adjust our systems we often change files that would
have
been stored in one place so they get scattered.
What's worse is when we install a file the system will naturally try
to write it to the first available space on the disk, if it can't
put all the file in the space available then it will move on to the
next available space
and continue there which is how we get file fragmentation. As it
does the
same with temporary files, you can see how easily it is for the
system to
get choked up with fragmented files and the more fragmentation there
is, the
more your drive heads have to jump about alll over the place to read
data
and consequently slowing your machine down.
When you defrag., what you are doing is re-uniting all the scattered
bits of
files so they are in one contiguous place: Starting at the beginning
of the
disk, it will find all the fragmented parts of a file and copy them
to empty
space, usually at the end of the disk. It will then do the same for
any
other files it needs to move to create a space big enough to write the
fragmented file back at the beginning of the disk but as one continuous
file. It will keep doing this until all the files have been trated
the same
way.
If it's possible to without causing an issue, I start it defragging
over
night, stop it when you need to use the machine then re-commence
when not
needed until the job is complete. I would then schedule an over-night
defrag. Once a week if you can. This weekly defrag. shouldn't be
too bad
since it'll only have one weeks mayhem to tidy up after, the
majority of the
files should be OK.
I use a programme called O&O defrag. which has a stealth mode,if it
finds
excessive fragmentation, it will defrag in background. This I find
extremely useful and allows me to not worry about defrag. Though I
should
add that I fell foul of it not long ago as it was active when I did
a hard
reset and that's how I corrupted my C drive. Having said that, I've
been
running it several years without a problem otherwise.
Hope that helps,
Paul
-----Original Message-----
From: jhb-bounce@xxxxxxxxxxxxx [mailto:jhb-bounce@xxxxxxxxxxxxx] On
Behalf
Of Peter Dodds
Sent: 02 January 2008 18:20
To: jhb@xxxxxxxxxxxxx
Cc: pdodds@xxxxxxxxxxxxx
Subject: [jhb] Re: Defrag
I've always assumed that if I stop it prematurely (which is quite
safe by
the way) it would start all over again when I restart it. I had a
laptop
once that always restarted a defrag every 10 minutes or so because
"new data
has been written to disk". I never found out what caused it and I
never
defragged that drive! (because I couldn't).
Peter
