Comment 20 for bug 570805
Revision history for this message
| Bela Lubkin (filbo) wrote Re: [regression] dpkg fsync cause massive regression in Ubuntu Server and Alternate installation times | #20 |
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35a32c5
(Get the code!)
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.