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# Clusters sizes

Posted on 2001-06-16
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I just got this partition magic program and I ran it on my HD.  I have 3 partitions, c ,d and e.  Now I came across one option in PQ and it said that my c drive has clusters size of 2k which has 7mb wasted of space.  And on my e drive, it has clusters size of 4k which has about 30mb wasted of space.  I was wondering what this means and if i can change it to 1k because the space wont be wasted as much.
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Question by:cooljam23

LVL 63

Expert Comment

Well, on a hard drive over 4 GB, unless you really are short on disk space, I would not fool with the cluster size.
With the price of a 30 GB hard drive at \$100, it just does not make any sense.

You will save a few megabytes on a GB drive, but you may cause future problems because of the non-standard cluste size.

If you need moew space, start Zipping your files with winzip or another compression program. Safer and more efficient !!

I hope this helps !

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LVL 12

Accepted Solution

Otta earned 100 total points
The FAT16 file-system was designed in the early 1980s,
when it was predicted that all hard-drives would be 32MB in size, or less.
So, one table uses 16-bit integers,
i.e., numbers ranging from zero to 65535,
and each entry in the table pointed to one "sector"
on the hard-drive.
Since each sector is 512bytes, do the math:
65536 sectors * 512 bytes/sector / 1024 bytes/Kbyte / 1024 Kbytes/Mbyte ==> 32Mb.

So, when you wrote a one-byte file onto the hard-drive, the other 511 bytes in the sector are "wasted".

Now that hard-drives are larger than 32MB,
the concept of a "cluster" was created,
i.e., one "cluster" is 2 or 4 or 8 or 16 or 32 or 64 consective "sectors" on the hard-drive.

Thus, the table now can point to hard-drives up to
64MB or 128MB or 256MB or 512MB or 1GB or 2GB,
per "partition" on the hard-drive.

Now, when you write a one-byte file onto the hard-drive,
the other N-1 sectors in the cluster are "wasted".

This is what Partition Magic is reporting.

One of the "advanced" options within Partition Magic can change cluster-sizes, within limits.
For example, if you create a 256MB partition,
it can be 65536 clusters at 8 sectors/cluster or
it can be 32768 clusters at 16 sectors/cluster or
it can be 16384 clusters at 32 sectors/cluster,
but it cannot use 4 sectors/cluster,
because that would result in too many clusters
to fit into a 16-bit number.

Play with Partition Magic, to see what resizing can be done with the specific partition-sizes you have.
P.M. has a "cancel" option, in addition to the "apply these changes" option.

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LVL 3

Expert Comment

Very well put Otta.

Other things to look at if you want to reduce wasted clusters is to look for tmp files, chk files, bak files, and any temporary internet files which you can safely remove.

Most of those files use only 1-10k.
After removing those files, use windows defrag so windows can free up any unused clusters.

a 1 k file will still use a 4k cluster hence 3k is wasted space.

Using otta's formula you can see it will add up.

I dont think 7mb of wasted space is all that bad.  Mine has 32mb of wasted space but nothing more can be done about it after cleaning up the drive. I wouldnt worry about it unless you are running out of free space, or suffering from performance issues.
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Author Comment

Thanks.
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LVL 12

Expert Comment

Note that the 'FAT32' file-system, introduced in later releases of Windows 95, and included in Windows 98 and Windows ME, uses 32-bit pointers.

Thus, there is much less need for "clustering",
when you have literally "billions" of pointers available,
rather than only 65536 pointers.

Partition Magic can convert from FAT16 to FAT32,
and you'll convert _SOME_ of that "wasted" space
into "free" space.
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