Re: [gentoo-user] Strange partition on USB stick

[Paul Hartman]

On Tue, Oct 4, 2011 at 1:39 PM, Mick <michaelkintzios@×××××.com> wrote:
> On Tuesday 04 Oct 2011 17:18:18 Paul Hartman wrote:
>> You can create a real partition table on that device and reformat, if
>> you want. (Note that some flash-based devices suffer degraded
>> performance if you repartition or reformat them because they come with
>> specially-aligned FAT tables from the factory)
>
> Interesting!  I didn't know that.
>
> I have repartitioned USB sticks in the past, but did not notice any change in
> performance - to be honest I didn't measure it.  I assume then that if I were
> to re-partition for any reason I would need to stick to exactly the same start
> & finish shown by parted.
>
> Re-formatting it ought to be OK though, as long as the fat16 shown by parted
> is correct.

I think filesystems other than FAT are aligned well already, assuming
your partitions are aligned, but with FAT there are some hoops you
must jump through.

There is a tool called flashbench that can test your drive
(destructively!) and figure out the most optimal block sizes. Here's a
great article about it and optimizing USB flash drives in general:
https://lwn.net/Articles/428584/

And here is a forum thread about figuring out the FAT alignment:
http://www.patriotmemory.com/forums/showthread.php?3696

The SD council makes a tool for MS Windows that optimally formats and
securely erases SD cards. Might be interesting to compare the results
of its format to a standard fdisk and mkfs.vfat in linux.

One thing I'm going to do next time I get a new SD card or flash drive
is take a snapshot of the boot sector/partition tables/FAT tables so
if I ever want to reformat it to FAT, I can restore the -- presumably
optimal -- factory layout.