[Bug 570805] Re: [regression] dpkg fsync cause massive regression in Ubuntu Server and Alternate installation times

[Bela Lubkin]

What benefit is provided by all the fsync action?

Without it, a power-failed install may have zero-length or wrong-content
files.

With it, a power-failed install still has a broken package -- each
individual file may be fully there or fully not-there, but there will be
missing files.

It doesn't help achieve a successful package install.  In fact, it
_increases_ vulnerability to power failures by making the vulnerable
time window more than twice as long (all of the added time is vulnerable
time, while some of the original time must be safe prep time).

Either way, system powers back on with a broken package.  Either way,
the user or the dpkg system must deal with it.

dpkg _should_ do a regular sync() after each package; I imagine (without
checking source) that it already does.  It already has notes on which
packages were in transition.  Make sure _those_ are fully sync'd,
fsync'd if that's the right way to do it -- those tell dpkg where to
pick up, which package to fix, after the power cycle.

I think this code should be retracted, even for normal post-install
package installs.  Cleanup is going to be needed after a mid-install
power failure either way; don't make users suffer through slow, noisy,
HD-punishing package installs for no [or negative] benefit.

-- 
[regression] dpkg fsync cause massive regression in Ubuntu Server and Alternate installation times
https://bugs.launchpad.net/bugs/570805
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