"Red Hat's adoption of ext3 is a first, tentative step
toward a journaling filesystem. When the company's plans became
known with its release of the second beta of its upcoming release,
Michael K. Johnson, chief of the company's kernel hackers, was
quick to provide a rationale.
"Why do you want to migrate from ext2 to ext3? Four main
reasons: availability, data integrity, speed, and easy transition,"
he wrote. Availability, he pointed out, involves quick recovery
from a system interruption rather than enduring e2fsck taking the
long way around. The journaling provided by ext3 makes avoiding
data corruption likelier. "Despite writing some data more than
once, ext3 is often faster (higher throughput) than ext2 because
ext3's journaling optimizes hard drive head motion," he wrote.
Perhaps the determining factor, though, was Johnson's fourth
reason.
"It is easy to change from ext2 to ext3 and gain the benefits of
a robust journaling filesystem, without reformatting," he said.
"That's right, no need to do a long, tedious, and error-prone
backup, reformat, restore operation in order to experience the
advantages of ext3."
Johnson said that Red Hat's choice was not meant to disparage
any of the other new filesystems, but instead was the most sensible
one for the biggest commercial distribution right now. Indeed, the
developers of the various journaling filesystems, too, have gone to
considerable lengths to avoid a holy war of the kind that erupts
frequently among backers of different projects that perform similar
functions.
"I personally think filesystems should be rewritten from scratch
every 5 years, but there are lots of people who think quite
differently on this," said Hans Reiser, for whom the Reiser
filesystem is named, in an email interview yesterday. "Reiser4 is
going to have a completely new core engine, and quite a lot of
people think that we should just make lots of tweaks to what we
have instead. It is extremely expensive, risky, and just plain hard
work, for us to do that core engine rewrite, and yet I think it
just has to be done. I could give you lots of logical reasons why
we are doing it, but those aren't the real reasons why we rewrite
when other filesystems don't. People just have different styles,
and fortunately both styles work in their way, each with different
effects and benefits."
