Comment 24 for bug 537241

Reopening this bug since -ubuntu4 has reintroduced it. It may not be as bad as before, since cjwatson said on irc that syncing is now only performed after unpacking all files in a single package, but I just tested upgrading beta 2 to current and the time to upgrade went from 6m21s to 11m15s.

To test I made a clean install of beta 2 to a new lv on my ssd, booted into the new install, ran apt-get update ; apt-get upgrade -d to download all the files needed. Then I booted back to my main install and made a backup of the test volume using dd. Booted back into test system and locked the version of dpkg to -ubuntu3 and ran a time apt-get upgrade -y. I then booted my main system and restored the dd backup, booted back into the test volume, and first upgraded dpkg to -ubuntu4, then again ran time apt-get upgrade -y.

It seems that this "fix" may be to solve a problem caused by people using data=writeback mount option on ext4, which is documented to be unsafe, and comes at a hefty cost to upgrade a number of packages at once. Because of this I feel this fix should be reverted.