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Default cluster size

Last response: in Windows XP
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December 2, 2009 2:28:20 PM

Hay everybody!
I saw this table at Microsoft website:

Drive size
(logical volume) Cluster size Sectors
----------------------------------------------------------
512 MB or less 512 bytes 1
513 MB - 1,024 MB (1 GB) 1,024 bytes (1 KB) 2
1,025 MB - 2,048 MB (2 GB) 2,048 bytes (2 KB) 4
2,049 MB and larger 4,096 bytes (4 KB) 8

my question is what the reason for this? what will happen if i will format a 100GB HD with cluster size of 512byts ?

More about : default cluster size

December 2, 2009 5:51:12 PM

Small cluster sizes work good if you have a lot of small files sizes as there is less waste. Large cluster sizes work good if you use large files.
Example.
On a 4,000 byte cluster drive a 2000 byte file will use one cluster with 2,000 bytes unusable. A 7000 byte file would use 2 clusters with 1,000 bytes unusable. The unused bytes in a cluster CAN NOT be used for other files hence the waste.
You would think then that a small cluster size would be best then - less waste. The trade off is slower drive access as the files can easily be placed all over the drive plus the overhead of maintaining a directory of all the clusters.
With drives the size they are today a 4000 byte cluster is fine as most files are going to be bigger than that.
Also, with larger than 4Kb clusters you can not use compression.
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December 3, 2009 3:46:36 AM

sturm said:
Small cluster sizes work good if you have a lot of small files sizes as there is less waste. Large cluster sizes work good if you use large files.
Example.
On a 4,000 byte cluster drive a 2000 byte file will use one cluster with 2,000 bytes unusable. A 7000 byte file would use 2 clusters with 1,000 bytes unusable. The unused bytes in a cluster CAN NOT be used for other files hence the waste.
You would think then that a small cluster size would be best then - less waste. The trade off is slower drive access as the files can easily be placed all over the drive plus the overhead of maintaining a directory of all the clusters.
With drives the size they are today a 4000 byte cluster is fine as most files are going to be bigger than that.
Also, with larger than 4Kb clusters you can not use compression.



I'm sorry but i don't understand you explanation on the 3rd paragraph. can you explain it in other words?
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December 3, 2009 9:18:16 PM

The drive has to keep a "table" also known as a FAT table - File allocation Table- of all the clusters that are on the drive and what files are in them.
The more clusters a drive has the larger the FAT table will be, the longer it will take to find the file.

Using smaller clusters means that a file will use more of them - 1 MB file on a 1000 Byte cluster size would use 1000 clusters to write the file. Those clusters could end up being spread out all over the drive.
That same file using a 32,000 Byte cluster size would only use 32 clusters - 31.25 to be exact but you must use the whole 32nd cluster. Those clusters may still be spread out over the drive but there are far less to have to read to get the whole file.
With the 1000Byte cluster size you don't lose any space with that 1MB file. With the 32,000KB cluster you end up wasting 24,000 Bytes of drive space. Multiply that out over several 100 or thousand files and you could easily lose several Gigabytes of space.

Take a look at some of the sites of this google search.
http://www.google.com/#hl=en&source=hp&q=drive+cluster+...
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December 4, 2009 10:56:35 AM

THANK YOU :) 
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!