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Journaling block device

JBD, or journaling block device, is a generic block device journaling layer in the Linux kernel written by Stephen Tweedie from Red Hat. JBD is filesystem-independent. ext3, ext4 and OCFS2 are known to use JBD.[1][2]

JBD exists in two versions, JBD and JBD2. JBD was created with ext3 in 1998.[3] JBD2 was forked from JBD in 2006 with ext4, with the goal of supporting a 64-bit (as opposed to 32-bit-only in JBD) block number. As a result, the maximum volume size in ext4 is increased to 1 EiB compared to 16 TiB in ext3 (assuming 4 KiB blocks).[4] JBD2 is backward-compatible. OCFS2 starting from Linux 2.6.28 uses JBD2.[5] The old JBD was removed with the dedicated ext3 driver in Linux 4.3 (2015).[6]

  1. ^ "The Linux Journalling API". The Linux Kernel documentation.
  2. ^ Kedar Sovani (June 20, 2006). "Linux: The Journaling Block Device". KernelTrap. Archived from the original on 2007-09-26.
  3. ^ Stephen C. Tweedie (May 1998). "Journaling the Linux ext2fs Filesystem" (PDF). Proceedings of the 4th Annual LinuxExpo, Durham, NC. Retrieved 2007-06-23.
  4. ^ Mingming Cao (9 August 2006). "Forking ext4 filesystem and JBD2" (Mailing list). Linux kernel mailing list.
  5. ^ "Linux 2.6.28". kernelnewbies.org. 2008.
  6. ^ Corbet, Jonathan. "rm -r fs/ext3". LWN.net.

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