Off topic- bytes per allocation unit

[Externet]

Hi. Sorry this is not electronics related...<p>¿How to FIND out how many bytes per allocation unit my hard drive being formatted has? Does it depend on the operative system? (Win98) or depends on the hard drive size? Or the file allocation table FAT 16/32 whatever that be ?
Is that user selectable? How? Which size is more convenient ?<p>Thanks,
Miguel

[bodgy]

Bytes per allocation unit is decided by the file format so FAT16/32/NTFS/Linux etc.<p>if you run chkdsk form the command prompt it will tell you your file allocation for the format you're running.<p>NTFS=4096 bytes per allocation unit.<p>Oh yes with FAT16 the size of the hardrive can matter. That is why when large hard drives first appeared 'those in the know' partitioned the HD into smaller logical drives - caused less defragmenting.<p>Colin<p>[ March 12, 2003: Message edited by: bodgy ]</p>

[chessman]

Ah yes...I remember back in the day when my parents tried to figure out what was wrong with the 8 gig hard drive showing up as 2

[Bob Scott]

Hi Externet,<p>It's been a few years since I knew this stuff like the back of my hand. We'll ignore FAT12, the ancient FAT (File Allocation Table) type of filing system designed before hard drives. The number of bytes per allocation unit is determined by the maximum number of allocation units available. With FAT16 this is 2^16, or 2 raised to the power of 16. This yields 16,536 possible allocation units on the hard drive. With large hard drives FAT16 becomes inefficient because the allocation units are so large. A small 20 byte file has to occupy at least one allocation unit which sometimes occupy thousands of bytes. Every file may use several units but the last one for every file is on average only half used and half empty. FAT 32 is a big improvement because it can divide huge hard drives into 2^32 number of units.<p>The HPFS filing system for the now obsolete OS/2 had fixed 512 byte allocation units. I don't remember how Unix types 83 and 84 (?) work.<p>Bodgy, are you sure NTFS uses such large units? I thought that NTFS was an offspring of the Microsoft developed HPFS.