[rrd-developers] two problem about RRD UPDATE

Florian Forster rrdtool at nospam.verplant.org
Sat Mar 21 09:47:56 CET 2009

Hi Lily,

On Sun, Mar 15, 2009 at 10:39:37AM +0800, lily wrote:
> How can I keep the data in memory? Use the mmap ? Is upgrade the
> version to 1.3.6 wil be OK  or I have to something in my code ?

basically, all you have to do is have more memory - the operating system
should do the rest..

> My rrdtool is the 1.2.27, I don't know if I upgrade my version to
> 1.3.6, Is there some *compatibility *problem ?

Version 1.3 introduces a changed file format. It can still work with RRD
files created by version 1.2, but not the other way around.

> > > You did mount with `noatime' and `nodiratime', right? While this doesn't
> > > perform miracles, it'll certainly increase performance some percent..
> Yes , I did not do that . But if I do that , I don't have the access
> time , rigth ?

Uhm, yes.. That's why it's called `NOatime'.. What do you need the
`atime' for? Are you sure you don't confuse this with the `mtime'?

I've heard of a system which relied on `atime' to clean up dynamically
created files (they were using the file system as some kind of cache,
really). When IO killed that system, they started deleting files a fixed
time after they were created (possibly recreating busy items/files),
which improved performance A LOT.

> Now I reduce the number of the file from 12K to 8K , I have not
> encountered the problem yet. So I think the reason is the high load .

I guess that your 12k files just do not fit into your 4 GBytes of RAM
and those 8k files to. I'd interpret this observation as indication that
more RAM is the easiest way out of your performance problems.

Florian octo Forster
Hacker in training
GnuPG: 0x91523C3D
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