Hi,
Les Mikesell wrote on 2009-07-07 12:17:56 -0500 [Re: [BackupPC-users] Hardware
considerations for building dedicated backuppc server]:
> Filipe Brandenburger wrote:
> > On Mon, Jul 6, 2009 at 23:57, Les Mikesell<lesmikesell AT gmail DOT com>
> > wrote:
> >> The only thing that seems slightly strange in the graphs is the load
> >> average
> >> going to 12 as the backups start and staying there a couple of hours.
> >> Normally
> >> that's the average number of 'other' processes that are waiting for CPU but
> >> otherwise runnable (i.e. not themselves blocked on i/o).
> >
> > I used to think that, but in fact processes that are blocked in disk
> > i/o (the ones in "D" state) do count in load average. So the load
> > average of 12 in this case probably means processes writing to the
> > disk.
>
> That must be a Linux quirk (bug?) but it does explain some numbers I've
> seen.
if it is, it's inherited at least from SunOS (and HP-UX, if I remember
correctly). I haven't been using Solaris for quite a while, so I can't say
if the load on NFS clients still goes up when NFS servers go down. SunOS 5.10
w(1) documents the load to mean "average number of jobs in the run queue",
which should *not* include processes waiting for I/O. Probably a Solaris quirk
(bug?) though.
Both ways of defining load make sense. Processes waiting for short term disk
I/O are using resources (and would probably be running if the disk was simply
faster). NFS I/O is not necessarily "short term", but that's a different
matter.
Linux uptime(1) documents what "system load" means on Linux.
Wherever it matters, you won't be looking at a single figure to measure your
system's state anyway.
> Regardless, there shouldn't be that many things running.
Yes, running BackupPC_nightly outside the backup window (as has already been
agreed upon) is definitely important.
Regards,
Holger
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