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From: Clark Smith on 13 Aug 2010 12:28
I have a Linux box that I occasionally use for backing up my
DVDs. I have noticed that for some DVDs the system load shoots up to 5 or
even higher, while the back-up process in place. The system becomes
sluggish at that point, some applications taking many seconds to launch.
However, the top command does not return any obvious information about
who is consuming all the resources.

What is going on? My guess is that it must be the kernel. But,
what is it doing? Does it take so many resources to back up a DVD?
Actually, I have noticed that anything that involves copying large
amounts of info to/from hard drive tends to be heavy on system resources
usage. Why is that the case? I mean, I understand that copying several
MBs from disk is probably nontrivial but, can it really be so bad as
render a modern system sluggish while bringing the system load to 5 or
higher?

From: Joe Beanfish on 13 Aug 2010 13:28
On 08/13/10 12:28, Clark Smith wrote:
> I have a Linux box that I occasionally use for backing up my
> DVDs. I have noticed that for some DVDs the system load shoots up to 5 or
> even higher, while the back-up process in place. The system becomes
> sluggish at that point, some applications taking many seconds to launch.
> However, the top command does not return any obvious information about
> who is consuming all the resources.
>
> What is going on? My guess is that it must be the kernel. But,
> what is it doing? Does it take so many resources to back up a DVD?
> Actually, I have noticed that anything that involves copying large
> amounts of info to/from hard drive tends to be heavy on system resources
> usage. Why is that the case? I mean, I understand that copying several
> MBs from disk is probably nontrivial but, can it really be so bad as
> render a modern system sluggish while bringing the system load to 5 or
> higher?
>

You don't want to create coasters instead of usable DVDs do you?
As I understand it you have to keep a constant data flow to the DVD
while burning to avoid a coaster creating under run condition. So the
system is dedicating many interrupts to ensuring that the DVD gets
it's data. Also, if this is IDE and your hard disk is on the same bus
chances are it will be able to do little to no other I/O while the backup
is going on.

BTW, top doesn't tell you much besides CPU usage. Your real problem is
disk usage which is the most common cause of high loads. Look at the
ps STAT column to see which processes are waiting for disk (D).
From: The Natural Philosopher on 13 Aug 2010 15:27
Clark Smith wrote:
> I have a Linux box that I occasionally use for backing up my
> DVDs. I have noticed that for some DVDs the system load shoots up to 5 or
> even higher, while the back-up process in place. The system becomes
> sluggish at that point, some applications taking many seconds to launch.
> However, the top command does not return any obvious information about
> who is consuming all the resources.
>
> What is going on?

your machine has filled its buffers and is in the process of flushing
data to disk, and has no spare RAM for applications untuil its finished.


My guess is that it must be the kernel. But,
> what is it doing? Does it take so many resources to back up a DVD?
> Actually, I have noticed that anything that involves copying large
> amounts of info to/from hard drive tends to be heavy on system resources
> usage. Why is that the case? I mean, I understand that copying several
> MBs from disk is probably nontrivial but, can it really be so bad as
> render a modern system sluggish while bringing the system load to 5 or
> higher?
>
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