Re: File systems on 4k sector devices?

[Taylor R Campbell <campbell%mumble.net@localhost>]

   Date: Thu, 7 Jun 2012 16:39:50 -0400
   From: Thor Lancelot Simon <tls%panix.com@localhost>

   On Thu, Jun 07, 2012 at 07:06:04PM +0000, Michael van Elst wrote:
   > 
   > But that also means that you cannot copy an encrypted image to
   > a disk with different geometry. Someone has decide wether that's
   > worthwhile. In that case you can either build a blocking/deblocking
   > layer into cgd (ugly) or define that larger blocks are split into
   > individually encrypted chunks of 512 bytes.

   I believe either way, there are atomicity issues.  A converter might be
   in order or, as Christos suggested to me privately, just require the
   user to mount both disks and restore the data through the filesystem.

What atomicity issues would there be in splitting larger blocks into
individually encrypted chunks of 512 bytes?

I think the cgd format, independent of the disk on which it is stored,
should just encrypt the data in 512-byte units.  Whether you do I/O
one 512-byte unit at a time, with 512-byte sectors, or four of them at
a time, with 4096-byte sectors, shouldn't change the sequence of bytes
that gets stored on the disk, and shouldn't be the difference between
a legible cgd image and an illegible one.