[syslog-ng] Trying to let my harddrive spin down once in a while
Paul Krizak
paul.krizak at amd.com
Tue Jul 12 01:27:20 CEST 2011
> I have a guarantee that it'll spin up every 10 minutes, forever,
> although there's absolutely no reason for it.
There absolutely is a reason for your disks to spin up -- applications
are sending messages to syslog-ng, and syslog-ng is dutifully trying to
write them to disk. If you aren't writing it out to disk, then what's
the point of running syslog at all?
If you really don't care about keeping the contents of your system logs
(and you should), you could always create a ramdisk in your startup
sequence (before syslog-ng starts up) and then mount /var/log to it.
Then writes to syslog wouldn't hit the hard disk, and your HDD can stay
spun down. Since you probably wouldn't want to waste much RAM on that,
you should probably also combine that with some modified logrotate
configuration and run logrotate hourly instead of daily, to ensure you
don't fill up your ramdisk with log data.
> I did, on the other hand, try running strace on syslog-ng and this
> is was I got just before my harddrive would wake up, every time:
> http://pastebin.com/raw.php?i=hFZVurBP
If you run strace with -s 1024 you'd be able to see the whole message
that is being written, but it looks like a cron message to me, which
makes sense. Cron wakes up regularly, and when it does, it sends a
syslog message. syslog-ng receives that message, and in the default
configuration, will promptly commit that message to the log on disk.
Honestly I'm not really sure what you're so concerned about here -- your
computer is always active doing *something*, even when you're not
actually sitting in front of it. Part of that is the system logging
activity, which has to be able to write to disk. If you're trying to
eke out every last watt from your laptop to enhance battery life, then I
would think that using an low-power SSD instead of a spinning disk would
be a better trade than trying to make your computer completely avoid
making disk accesses when idle.
Paul Krizak 7171 Southwest Pkwy MS B200.3A
MTS Systems Engineer Austin, TX 78735
Advanced Micro Devices Desk: (512) 602-8775
Linux/Unix Systems Engineering Cell: (512) 791-0686
Global IT Infrastructure Fax: (512) 602-0468
On 07/11/2011 01:02 PM, Lars Stokholm wrote:
> What do you mean by it's internal log messages? These?
> destination d_syslog { file("/var/log/syslog.log"); };
>
> flush_timeout worked perfectly. I tried to set it to 10 minutes and
> that's exactly how long my harddrive was allowed to stay spun down.
> But on the other hand I have a guarantee that it'll spin up every 10
> minutes, forever, although there's absolutely no reason for it.
>
> I didn't try removing all the log paths, since I was not sure exactly
> how I was supposed to do it and since it's not really clear to me what
> I'll gain from it. :)
>
> I did, on the other hand, try running strace on syslog-ng and this is
> was I got just before my harddrive would wake up, every time:
> http://pastebin.com/raw.php?i=hFZVurBP
>
> What can you make from this strace output? The same pattern was
> repeated again and again. I guess "/usr/sbin/cr" is the cut-off path
> to crond.
>
> On Mon, Jul 11, 2011 at 8:49 PM, Paul Krizak<paul.krizak at amd.com> wrote:
>> Are you doing anything with syslog-ng's internal log messages? It's
>> maintaining counters and such internally that I believe get written out
>> to disk by default once per minute.
>>
>> But since that's a normal log path, that should be controlled by
>> flush_timeout() as well.
>>
>> Start by trying the flush_timeout() setting, and if that works, then at
>> least you know that is something in a log path somewhere causing the
>> trouble.
>>
>> Another thing you could try is removing all of your log paths (not just
>> routing them to /dev/null) and see how syslog-ng behaves.
>>
>> Finally, if you still can't nail it down, use strace to trace syslog-ng
>> during a period where it causes the disks to spin up. You should be
>> able to at least see the file it's trying to write. For example, it
>> might be updating its pid file in /var/run once per minute.
>>
>> Paul Krizak 7171 Southwest Pkwy MS B200.3A
>> MTS Systems Engineer Austin, TX 78735
>> Advanced Micro Devices Desk: (512) 602-8775
>> Linux/Unix Systems Engineering Cell: (512) 791-0686
>> Global IT Infrastructure Fax: (512) 602-0468
>>
>> On 07/11/2011 11:33 AM, Lars Stokholm wrote:
>>> And I forgot to add to that, that killing syslog-ng, but keeping crond
>>> alive, will also allow my harddrive to stay spinned down, so this is
>>> not crond's fault. As soon as I start syslog-ng I see log entries in
>>> trace_pipe and my disk starts to wake up a lot.
>>>
>>> On Mon, Jul 11, 2011 at 8:28 PM, Lars Stokholm<lars.stokholm at gmail.com> wrote:
>>>> I see, that makes sense. Thanks. I would also like to avoid it if
>>>> possible. But in order to avoid it, I have to find out why this is
>>>> happening:
>>>>
>>>>>>>>>> As you can probably see, syslog-ng writes every minute at least. I guess
>>>>>>>>>> that's because my user crontab has a command that gets run every minute.
>>>>>>>>>> What I don't get is why syslog-ng writes to the disk, even though I'm
>>>>>>>>>> telling it not to log crond's output.
>>>>
>>>> Any ideas? As you can see from my syslog-ng.conf, everything that has
>>>> to do with crond is sent to /dev/null. So crond output shouldn't cause
>>>> a spin-up of my harddrive, but it does. Killing crond or removing the
>>>> once-per-minute-command from my user crontab will allow my harddrive
>>>> to stay spinned down for a long period of time. But I would rather not
>>>> do either.
>>>>
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>>>
>>
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>>
>>
> ______________________________________________________________________________
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