[Bug 593086] Re: Silent wraparound on > 2 TB disks

[Phillip Susi]

Seems CONFIG_LBDAF was barking up the wrong tree.  It is set on the i386
build, and does not apply to amd64.


** Summary changed:

- Need CONFIG_LBDAF set to prevent silent wraparound on > 2 TB disks
+ Silent wraparound on > 2 TB disks

** Changed in: linux (Ubuntu)
       Status: Triaged => New

** Description changed:

  Ubuntu kernels silently wrap access to disk locations above 2 TB back
  around to zero.  This can easily be reproduced using lvm to create a
  thin provisioned virtual disk:
  
  lvcreate --type zero -L 3t -n empty vg0
  lvcreate -s -n thin vg0/zero -L 1g
  
  mke2fs -t ext4 -E lazy_itable_init /dev/vg0/thin
  e2fsck -f /dev/vg0/thin
  
  Fsck will find errors in the bitmap because it is actually reading the
  superblock instead of the allocation bitmap situated just after the 2 tb
- mark.  I emailed the dm-devel mailing list about the issue and was told
- that this happens when CONFIG_LBDAF is not set, and that it would be
- rather daft of a distribution not to set that option.  I checked my
- config for kernel 2.6.32-22-generic on lucid amd64 and indeed, this
- option does not seem to be there.  I also first observed this bug on
- i386 karmic.
- 
- I believe that this bug effects all users who have a > 2tb disk, be it
- virtual, physical, or raid, and can lead to unexplained loss of data.
- Therefore I feel it meets the criteria for a high priority bug, if not
- critical.
+ mark.

-- 
Silent wraparound on > 2 TB disks
https://bugs.launchpad.net/bugs/593086
You received this bug notification because you are a member of Kernel
Bugs, which is subscribed to linux in ubuntu.