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SubjectRe: fsync on large files
On Fri, 12 Feb 1999, Alan Curry wrote:

> I'm coming late to this topic, but with a good reason: I just figured out
> today that syslogd's fsyncs have been the cause of some major performance
> problems on an ISP's central server. Load averages have been unreasonably
> high and gradually getting worse. Today we realized that there is a weekly
> cycle to it, and it matches the cycle of the log rotation of
> /var/log/messages. As this log file grows (currently 36 megs with 2 days left
> before rotation) and beyond, with syslogd fsync'ing every line it writes,
> syslogd hangs for long periods of time, and when syslogd is hung, lots of
> other stuff hangs.
>
> Previously I deleted all the messages on the large-file-fsync thread without
> paying much attention, and now it seems to have died off just when I realized
> I needed it. What I could find in the archive did not seem to be a conclusive
> answer to what is now a pretty urgent question: would 2.2.1 do better than
> 2.0.36 is doing here? And if I'm 2.2-phobic (which I'm not, but some people
> are), will 2.0.37 fix this problem?
>
> Given that all of the stuff on this machine is pretty close to redhat 5.x
> standard issue, including the syslogd and log rotation configuration, are
> there lots of other people out there suffering without knowing the cause,
> like I was?

There's no way in hell I'd run syslogd with fsync() enabled on a machine
that longs anything more than 1 line per minute. Disable fsync()ing in
syslogd by prepending "-" to each log file you want to turn it off for.

Simon-

| Simon Kirby | Systems Administration |
| mailto:sim@netnation.com | NetNation Communications |
| http://www.netnation.com/ | Tech: (604) 684-6892 |


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