Comment 3 for bug 556621

On Thu, Apr 08, 2010 at 04:00:34AM -0000, Phillip Susi wrote:
> Just tested installing lucid beta 2 to a 1.5 TB WD15EARS drive from a
> liveusb and setting this option in /etc/mke2fs.conf cut the install time
> in HALF. Without the option 5.5-6 minutes are spent sitting at 5%
> complete with no visible progress while mkfs runs, for an 11+ minute
> total install. After setting the option, the time spent in mkfs drops
> to ~15 seconds and gives just over 6 minutes total time to install.
>
> If this option is not set as a default in mke2fs.conf, then ubiquity
> should at least consider specifying it when calling mke2fs.

It's safe to use lazy_itable_init on brand-spanking-new disks. It's
safe if you are reformatting an existing partition, AND you never have
any errors in the block group descriptors that cause the block group
checksums to be invalid during the life of the file system.

If there are invalid block group checksums and a previous file system
is reformatted using lazy_itable_init, e2fsck can get confused with a
inodes from previous file systems. This is why the default is zero
out the entire inode table.

Given that Ubuntu users tend to be, ah, less sophisticated, and _very_
loud about complaining on Launchpad when things go wrong in confusing
ways, I can't really recommend enabling lazy_itable_init by default in
the Ubuntu installer at this time. There are some kernel development
work that I have planned that will make it be safe, but that work
hasn't happened yet.

      - Ted