[Mailman-Developers] Problem with MM after power outage
harald.meland at usit.uio.no
Fri Sep 12 18:50:28 EDT 2003
> Except that when I did some very simple tests, I saw a 97% hit in
> performance with fsync turned on.
Ouch. That's pretty severe, all right.
Even though I would *guess* that most "casual" Mailman sites would
pull through an effective halving of performance without any problems,
that is merely a guess... thus, I'm not at all sure that set of sites
that would be in trouble with such a big performance hit is disjoint
from the set of sites that don't read upgrade documentation very
> This on a RH9, ext3 Linux box of the Dell Optiplex variety. That
> makes me very nervous to add in a patch release that won't have any
> beta testing.
I hadn't considered the "no beta testing" part of this.
Reconsidering now, I agree that such a big performance hit in a
"bugfix" release ought to be the cause of quite a bit of nervousness
on behalf of the release issuer... :-)
> I'm happy to re-address this for the next major release, but for
> 2.1.3 I don't want to enable fsync by default, and I definitely
> don't want to do any probing/guessing of filesystems, etc.
That sounds like a good plan to me.
However, I'm not sure I understand why this shouldn't be configurable
in mm_cfg; is that just to keep the number of configurable variables
FWIW, PostgreSQL exposes an "do fsync(2)" option in it's global config
file; on my Debian system, the option is preceded with this comment:
# A special note on FSYNC:
# FSYNC only affects writes to the WAL (Write-Ahead Log). Turning it
# off will give some increase in performance, but at the risk of data-
# corruption in the event of power failure or other disaster. It is on
# by default. I strongly recommend you not to turn it off.
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