Paul Clements wrote:

quoted

   Is 16 blocks a large enough area?

Maybe. The superblock will be between 64KB and 128KB from the end of the
partition. This depends on the size of the partition:

SB_LOC = PART_SIZE - 64K - (PART_SIZE & (64K-1))

So, by 16 blocks, I assume you mean 16 filesystem blocks (which are
generally 4KB for ext3). So as long as your partition ends exactly on a
64KB boundary, you should be OK.

Personally, I would err on the safe side and just shorten the filesystem
by 128KB. It's not like you're going to miss the extra 64KB.

Or, better yet, shrink it by 1Mb or even 10Mb, whatever, convert
to raid, and - the point - resize it to the max size of the raid
device (ie, don't give "size" argument to resize2fs).  This way,
you will be both safe and will use 100% of the available size.

/mjt