Those following the progress of the Fedora 18 development cycle cannot have
failed to notice that the
, the distribution's installer,
is not going as smoothly as one might have liked. Complaints
and there is a real risk that installer problems will end up being what
users remember about this release. Given that, it may seem surprising that
the Fedora developers intend to change one of the fundamental decisions
made by the developers of the new installer.
The logical volume manager (LVM) sits above the block layer, providing
abstract storage devices that can be resized, encrypted, and more.
In the absence of explicit instructions to the contrary, Anaconda has
installed systems using LVM for many years. LVM adds some flexibility to
an installed system and supports a number of official Fedora features, but
it has the potential to confuse users who are not prepared for the
addition of a layer of indirection over their disk partitions. It also
irritates users who know they don't need LVM and would rather not see
another layer of software in the block I/O path. Grumbling about the use
of LVM in Fedora is not uncommon.
The new installer changes the default; unless the user asks for LVM
explicitly, current F18 testing releases will install directly onto disk
partitions and leave LVM out of the picture. How that change came to be is
not entirely clear; it does not seem that there was much, if any discussion
in the Fedora development community first. That did finally begin,
though, on October 25, when Adam Williamson filed a Fedora bug
asking that the change be reverted so that Fedora would, once again,
install and use LVM by default.
That discussion got off to a bit of a rough start; arguably, Adam's
phrasing did not help matters:
It's kind of hard to really swing the 'LVM annoys people' argument
too. Well, it _does_, but not for very good reason. That argument
boils down to 'catering to idiots': the people who say they're
annoyed by LVM as default are people who know raw partitioning,
don't understand LVM, and are resisting change.
In the end, though, the real arguments in favor of changing Anaconda to
came to the fore; there are several of them. The first of these is that a
number of advertised Fedora features depend on LVM; a user who does without
LVM will end up without the ability to use System
Storage Manager, resize filesystems, migrate filesystems across disk,
and more. Thus, Ric Wheeler said,
turning LVM off by default constitutes a regression that needs to be
There is also the little problem that Fedora's documentation is written
with the assumption that LVM is in use. Turning LVM off obsoletes that
documentation without fixing it. Quality documentation is hard enough to
come by as it is; causing what documentation exists to become inaccurate
without (as LVM proponents see it) a proper justification just makes things
worse to no good end.
Also relevant is that the
current plan is for Fedora to switch to Btrfs during the Fedora 19
development cycle. Given that, making a fundamental change to the Fedora
storage stack now makes little sense to many developers. It will just add
churn to a system that is going away anyway, leaving one Fedora release
with a storage setup that differs from all the others. That has the
potential to confuse users and increase the amount of work the Fedora
storage developers have to put into supporting the F18 release. Even if
the Btrfs transition is delayed to F20 (an outrageously shocking and
unpredictable course of events, but one might as well ponder even highly
unlikely scenarios), a case could be made that it might be better not to
perturb the existing stack unnecessarily in the meantime.
Finally, it has been pointed out that the change to Anaconda returning it
to the pre-F18 default is quite small;
it is really just changing the default value of a checkbox on an installer
screen. All of the code for installing over LVM — code that has been used
for many releases — is still there and working as well as ever. So the
change should be safe and should not be cause for yet another slip in the
Fedora 18 schedule.
Arguments for leaving the default as it is (and, thus, continuing to
install without LVM) usually start with the fact that
it is quite late in the F18 development cycle; unnecessary changes — even
small and seemingly safe changes — should be avoided if possible. That is
doubly true for the installer, which has had trouble stabilizing as it is.
Rather than revisit established decisions, it is said, it would be better
to focus on fixing the known problems and getting a solid release out the
Beyond that, some developers question the value of LVM. Fedora developer
Resizing partitions isn't that common and not the primary use of
LVM (you can do it without it and most users won't). It is still
pretty much useless (as in the extra features won't be used) for
the average desktop / laptop installs. For most users all it does
is slowing down the boot process (we should stop adding crap to the
default boot process because someone might need it on some obscure
LVM has been fingered in the past for slowing down the boot process;
indeed, it has been called out as
one of the chief offenders. Discussion in the bug report suggests that
LVM's dependency on udev-settle, which is the real cause of
boot-time delays, has been significantly reduced, to the point that many or most
installations no longer need it. But, if boot time is a prime concern, the
addition of another service to set up in the boot path is unlikely to help
Finally, opponents argue that LVM is confusing to relatively
unsophisticated users who will end up being unable to manage their systems
properly. It is an added level of abstraction that makes things harder
without bringing any significant new value. It would be better, they
argue, to behave like many other distributions and just install directly
onto disk partitions by default.
The Fedora Engineering Steering Committee (FESCO) took up this issue and
brought it to a vote on October 30. Full consensus was not to be
found there either, but, in the end, FESCO voted in favor of the change
back to the pre-F18 default.
So, unless something gets derailed somewhere, the Fedora 18 will, like
its predecessors, install and use LVM by default.
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