Re: [aclug-L] Scandisk

[Bob Deep <bobd@xxxxxxxxxxxx>]

Jeff wrote:
> 
> On Wed, 18 Nov 1998, Leon Do wrote:
> 
> > Does anyone know which tools that I can use to scan my hard drive
> > problem and defragmentation?
> 
> I know fsck gives you an idea of fragmentation, but I don't know about
> scanning for bad blocks. I'd be interested in this, as one of my
> drives is having problems. Is there a program that can run on a
> partition/drive (unmounted of course) that will scan & flag bad
> sectors?  BTW, there is a 'defrag' program that I found, but it's
> chock full of "warning: this might do really bad things, use at your
> own risk" kinds of things.  It actually does go through and do like
> that one Windows program where it rearranges the files. I haven't used
> it (haven't needed to).

Two things...  First, Unix file systems don't suffer from problems with
performance due to fragmentation (unless the partition is *very* full
and files start getting fragmented).  Unlike the old Dos model, where
you always use the lower sectors first, Unix file systems generally
don't fragment the files if it can be helped.  This is what I understand
anyway...  So you don't usually need to defragment files on a unix
box...

Second... Unless you are running a very old MFM drive or something,
scanning the hard drive for bad blocks is not going to do you much
good...  IDE drives usually re-map arround bad sectors and you won't
ever know it... I beleive SCSI is about the same.  Now Old MFM drives
needed the bad sectors marked (usually you hand entered the sectors
marked on the drive lable)...  If you are getting new bad sectors,
chances are your drive is *very* close to giving up the ghost, or you
are seeing the results of a kernel file system bug...

If you insist on scanning your drives, I would point out, that your
drives will be automaticly scanned prior being mounted every so many
times (Don't know how many though), and usually they will be scanned and
repaired if they where improperly dismounted, so if you watch the boot
messages you will catch any errors as they are found...

So..  Don't bother with the defrag idea.  It's not likely you would ever
need to do it, or notice any performance gain if you did.

If you want to scan a drive use fsck...  I think it only checks the file
system for consistantcy, but witn an IDE drive, it is very unlikely you
will have bad blocks to find anyway.  You can scan a partition for bad
blocks at format time, but I don't know if you can do it on a partiton
in use.  The bottom line on bad blocks is... If you are seeing new bad
blocks, time to shell out some $$ for a new drive...

-= Bob =-
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