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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 Kirby | Systems Administration |
    | | NetNation Communications |
    | | Tech: (604) 684-6892 |

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