Wiping hard disk

[Bill Ridgeway]

Can wiping the slack area of a hard disk free up disk space? It doesn't
seem logical but I have done so and disk usage has decreased by 3Gb. I am
concerned that it has also taken out some files but seems to be working OK.

Thanks.

Bill Ridgeway
Computer Solutions

 

[Bob I]

No. The "slack space" is already "empty".

 

[Noncompliant]

Can you clarify exactly what you did based on what slack space is defined
as?

http://www.pcguide.com/ref/hdd/file/part_Slack.htm

 

[Bill Ridgeway]

Thanks. That's what I thought but it was strange to loose 3Gb immediately
after a wipedisk especially as I haven't uninstalled or deleted anything!

Regards.

Bill Ridgeway
Computer Solutions

 

[Bill Ridgeway]

I used the 'Secure Delete' function of 'Advanced System Optimizer' to 'Clean
Free Space Only -Secure Delete - American DoD 5220.22-M'.

Regards.

Bill Ridgeway
Computer Solutions

 

[Noncompliant]

And how does that affect slack space?

 

[Bill Ridgeway]

I can't see how wiping slack space would have affect disk usage but as this
was the only thing that happened (I didn't uninstall apps or delete file)
between it being 11.5Gb and 8.5Gb the logical working conclusion is that it
affected disk usage in some way - which is why I asked the question in the
first place.

Regards.

Bill Ridgeway
Computer Solutions

 

[Bob I]

Perhaps what XP considers free space and what the Application considered
free space is the cause. Is your recycle bin still working correctly?

 

[Bill Ridgeway]

Yes. It's cleared out everyday.

I recall (some while ago) something to the effect that the actual amount of
space taken on a hard disk has to be in multiples (?of what) so each file
has a small amount of free space between its actual size and the amount of
space taken on the hard disk. I don't know if that is pertinent here.

Regards.

Bill Ridgeway
Computer Solutions

 

[Bill Blanton]

What you may be recalling is clusters. Files are stored in clusters which
are multiples of HDD sectors. If, for example, your file system is using
4K clusters(2 sectors), then a 1 byte file will use 1 4K cluster, with 4K-1byte
being the slack. A 4096 byte file will have no slack (4K-4K). A 4097 byte file
would have the same slack as the 1 byte file. 4K*2clusters-4097.

Zeroing out file slack should have no bearing on the free space
count. If the volume was FAT32, it's possible that the app corrected the
free cluster count held in the boot sector. If NTFS, I believe the count
is taken from the volume's cluster $Bitmap file.

 

[Bill Blanton]

Correction: 4K clusters will use 8 - 512 byte sectors, not 2. I mathed
backwards or something... :-/

 

[Bill Ridgeway]

Thanks to Bill and other contributors. Bill wrote <<it's possible that the
app corrected the free cluster count held in the boot sector.>> For now I
will accept that supposition as being likely. It's either that or putting
this down to one of those mysteries in life.

Regards.

Bill Ridgeway
Computer Solutions

 

[Noncompliant]

Yes, that's your contention. But, I don't see where you arrive that its
affecting slack space... How did you come to that conclusion?

 

[Noncompliant]

There's actually more than 512 bytes in a common sector. The 512 bytes
portion is used for storage. That's all the OS can see of it.

 

[Bill Ridgeway]

Easy. It was 11.5Gb before and 8.5Gb after wiping. Ergo, wiping freed up
3Gb. It is that assumption that I am questioning!

Regards.

Bill Ridgeway
Computer Solutions

 

[Bill Blanton]

Thanks. Correct. Iin this context, as it relates to file system clusters.
"Logical" sector if you like. There's also a move to increase this from the
current 1/2K to 4K.

 

[Noncompliant]

Well, that's why I previously provided the defintion of slack in a weblink
on a previous reply. If the cluster size is the same, the slack space
should not have changed.