#10911 NORM Future : ubifs images are significantly bigger than jffs2 (was: investigate XO-1 build growth)

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#10911: ubifs images are significantly bigger than jffs2
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           Reporter:  dsd           |       Owner:  dsd           
               Type:  defect        |      Status:  new           
           Priority:  normal        |   Milestone:  Future Release
          Component:  build-system  |     Version:  not specified 
         Resolution:                |    Keywords:  dsd-11.3.0?   
        Next_action:  never set     |    Verified:  0             
Deployment_affected:                |   Blockedby:                
           Blocking:                |  
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Changes (by dsd):

  * keywords:  => dsd-11.3.0?
  * type:  task => defect
  * component:  distro => build-system
  * milestone:  11.2.0-final => Future Release


Comment:

 Hijacking this ticket to something more specific now that I've made a key
 finding: jffs2 uses zlib compression by default, ubifs uses lzo (which is
 faster, but doesn't compress as well)

 Here are my experiments of creating jffs2/ubifs filesystems with different
 parameters starting off with 11.2.0 xo-1 os20.tree.tar.lzma:

 {{{
 LZMA tarball os20: 476mb
 jffs2_default.img: 634mb
 jffs2_default.img after sumtool: 664mb
 ubifs_default.img (LZO): 713mb
 ubifs_zlib.img: 647mb (i.e. created with -x zlib)
 ubinized zlib: 668mb
 ubifs_favor_lzo.img: 689mb (i.e. created with -x favor_lzo)
 }}}

 If we switch to zlib for ubifs (to be consistent/comparable to our jffs2
 setup), the numbers to compare are "jffs2_default.img after sumtool" vs
 "ubinized zlib" (as these are effectively the bits that get flashed to
 disk). As the numbers are basically equal it means that particular problem
 is solved.

 I plan to switch ubifs image creation over to zlib but make it
 configurable in olpc-os-builder.

-- 
Ticket URL: <http://dev.laptop.org/ticket/10911#comment:5>
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