Tracing Disk Activity
cswiger at mac.com
Mon Nov 22 09:12:56 PST 2004
On Nov 21, 2004, at 2:17 PM, Hanspeter Roth wrote:
> On Nov 21 at 10:50, Chuck Swiger spoke:
>> Hanspeter Roth wrote:
>>> I have set an idle timeout for the hard-disk. But when there is no
>>> user activity there are frequent disk accesses.
>> Yes, this is Unix. Even when there is no user activity, a Unix system
>> normally is still running a number of daemons such as syslogd which
>> regularly write to the filesystem. Beyond that, the syncer mechanism
>> to reduce the number of dirty memory buffers every thirty seconds or
> I guess that some daemons are causing disk access. But it must be
> not only syslogd.
That's right. Normally, people end up running a number of daemons like
sendmail or some other MTA, ntpd, named, etc.
> Is the syncer causing the disk to spin up even if there is nothing to
Probably no. However, if you have active processes running on the
system, it is very likely that the syncer will find data that it does
want to write.
>> Instead you probably will need to mount filesystems read-only and
>> RAM disks in a fashion similar to booting off limited-write media like
> My idea is to transfer those files that are written also when the
> user is idle to a RAM disk (some from /var/log and dhclient.leases).
> But I don't want to mount the filesystems read-only.
OK. However, you are probably not going to be able to prevent
everything running on a normal Unix system that wants to scribble to
disk short of heroic measures.
>> Compact Flash. Either that, or simply shutdown the system or run zzz
>> suspend the system via APM/APCI.
> This is less convenient and probably doesn't work on my laptop. (I
> have to check whether the upgrade to 5.3R has changed something in
> this respect.)
Hmm. For what it is worth, it's taken about two years of effort by
Apple to work through many of these issues in order to get MacOS X on
their laptops to be reasonably friendly in terms of saving power,
conserving hard drive access, and having power save/suspend to RAM
More information about the freebsd-questions