Flash Drive alignment

[zankit]

Hi what is the best alignment for a Sandisk Ultra backup 32GB thumb drive. The drive shows as a fixed drive. I'd like to format it as NTFS with 4Kb cluster size

 

[TheLastDoomguy]

Partition alignment and cluster size have very little to do with each other.

 

[zankit]

How to determine the erase block size of a flash drive?. Many says 128Kb is the default erase block size of NAND flash drives and aligning it with 128Kb reduces write cycles thereby increasing performance and life of the drive. Is this true?
Please share some detailed information.

When I bought the SanDisk ultra backup it was FAT32 16K cluster size and displayed 29.8GB free space. I accidentally deleted the partition in windows disk management and after that it shows 29.7GB free space in FAT32. But if format it in FAT32 with 32KB or higher cluster size it shows 29.8GB why is that?

 

[TheLastDoomguy]

Because the file allocation bitmap is half the size (32KB clusters vs 16KB clusters = less clusters to track in the bitmap = bitmap is half the size).

Therefore there is 'more' space available to actually 'store' files.

That said, each file will be rounded up to the nearest 32KB block, so the space you gain from doing it may be 'lost' in "file slack" later.

With 128KB clusters, every file would be rounded up to the nearest 128KB in size.
For storing files that are exact multiples of clusters (such as 1GB files) this is never a problem, and you're better off using 32KB or 64KB clusters.

IMHO anything larger than 64KB is just wasteful, and anything smaller than 4KB causes too much micro-management of the file allocation bitmap. (2KB vs 128KB would have the bitmap being 64 times the size... and this may equate to gigabyte sized bitmaps on large enough drives).

4KB to 64KB is the 'happy zone', where you get good storage usage, and good performance from large clusters without being wasteful.

Most flash devices have a wear leveling mechanism or similar logic anyway...

 

[zankit]

How to determine erase block size?. Can it be calculated from parameters like number of sectors, heads, cylinders, tracks etc?