Holger Parplies wrote:
> Paul Harmor wrote on 01.01.2007 at 20:51:43 [[BackupPC-users] OK, how about
> changing the server's backuppc process niceness?]:
>
>> I have only 2 machines (at the moment) being backed up, but every time
>> the backups start, the server system slows to an UNUSEABLE crawl, until
>> I can, slowly, start top, and renice the 4 backuppc processes.
>>
>> Any way to make them start nicer, to begin with?
>>
[...]
> I wouldn't be surprised, though, if your problem is either not CPU related
> or caused by a misconfiguration if it really is. Please someone correct me
> if I'm wrong, but a 1.3 GHz Duron doesn't sound slow enough by far to me to
> be legitimately overloaded by 2 backups. 512MB of memory maybe, but renicing
> wouldn't help then, would it?
>
> Have you tried what happens, if you only run *one* backup at a time
> ("$Conf{MaxBackups} = 1;")?
>
>
Good recommendations, Holger. I would add that "nice"ing a process only
changes its scheduling affinity, but does not modify in any way its hard
disk activity or DMA priority, so until the original poster understands
what exactly makes the server slow, he's shooting in the dark. A busy
hard drive usually makes a system feel slower than a busy CPU process,
because hard disk activity requires a 6-10ms seek minimum, plus
streaming and unloading to vram, depending on what other processes are
doing.
Personally, I dedicate a Pentium Pro 200mhz with a whopping 128mb of
ram, and it backs up about 130gb across four machines, all starting
about at the same time, using rsyncd on 3 and SMB on 1. It's true the
CGI interface is slow to respond during two simultaneous backups, but
otherwise it's usable. I wouldn't put another app on that machine,
though, for obvious reasons.
IMHO, the original poster would do well to diagnose what bottleneck is
the culprit before attempting to fix it. My suggestions, to help reduce
the CPU usage further, is to drop compression to 0. That should be
about all that BackupPC would spend a lot of time on during a backup.
But my PPro200 can handle level 3 compression; a >1Ghz Duron will too.
JH
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