I am trying to format a brand new 1TB Western Digital blue mechanical hard drive using Windows 7 Disk Management. It is not giving me the option to select an allocation unit size less than 4096 bytes, but on the two other mechanical hard drives that I just formatted (500 GB and 750 GB), it gave me the option to select greater than or equal to 512 bytes. Is there something about the 1 TB size that prevents me from selecting less than 4096 bytes for allocation unit size?

Thank you.

  • 2
    Unless you intend to create/use a lot of small files and have very few large files (large in relation the cluster size, e.g. greater than 20 times), a small cluster size will probably hinder filesystem performance. There's only a small benefit of reducing wasted disk space. And if you're going to allocate the entire 1TB disk to just one partition with undersized cluster, then you're really asking for a performance hit. – sawdust Sep 12 '13 at 7:41
  • Not only what @sawdust mentions, but by using a smaller cluster size you would also use more space for the file system metadata, which can lead to a net loss of available disk space for user files compared to using a larger cluster size with the same use case. Everything that deals with allocated clusters will need 8x the space if you use 512 byte clusters rather than 4096 byte ones, and while that won't grow the overall file system metadata size by 8x, it will likely cause a marked increase in the amount of bookkeeping metadata required. – a CVn Sep 12 '13 at 8:17
  • Your new drive probably has a sector size of 4096 bytes, and the smallest unit of allocation is one sector. – sawdust Sep 12 '13 at 8:21
  • @H3br3wHamm3r81 - Why do you persist in writing the cluster sizes in units of "MB" (megabytes) rather than bytes??? – sawdust Sep 13 '13 at 0:14
  • @sawdust: I'm not persisting. I didn't notice your edit until after I made that comment, and even then, I forgot to edit my comment. Sorry about that. – user76275 Sep 13 '13 at 3:06

It's a requirement for drives larger than 2TB but as far as 1TB goes, it's not a strict requirement. This is due to a number of factors including MSDOS/MBR versus GPT. Do you have a specific reason to use 512 byte sectors?

Anyway, Linux to the rescue, just boot the GParted LiveCD and format the drive that way.

You'll want to delete the drive's existing partition table, create a MSDOS partition table and then create your partitions. You'll want NTFS partitions for Windows.


new partition table

format partition

  • Check the question again; I believe you are answering the wrong question. The question is about the allocation unit (cluster size), not the sector size. And NTFS does not have the same constraints that do FAT. – a CVn Sep 12 '13 at 8:15

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