Re: [Vserver] Wiki : HowTo graph vserver usage with cacti

From: Grzegorz Nosek <>
Date: Fri 16 Dec 2005 - 14:56:56 GMT
Message-ID: <>


2005/12/16, GarconDuMonde <>:
> me also! i really don't know that much about kernel stuff at all, and it's not
> highest on my list of priorities to learn at the moment, but i am keen to
> "monitor the hell out of the vservers" (what a great phrase!), ultimately on a
> number of different physical hosts. currently, the only monitoring tool i really
> have experience with is munin, but cacti has been highly recommended to me, so
> i'm very happy to learn it and then try to help get it as good as possible for
> vserver usage.

We're actually using an in-house monitoring tool (similar to munin or
cacti but better suited to our needs) but the overall idea is very
similar (get data via snmp and graph it).

> err, did you patch the kernel to collect the usage stats? as i said, i know zero
> about kernel stuff, really, but would have thought that hte more patches to the
> kernel, the more insecure; and that it would be better to monitor from some
> other method.

Yep, but I don't like the patch. Due to various implementations of
filesystems (tested on ext2, ext3 and reiserfs) I couldn't use
current->xid (the context of the current process), as the journaled
filesystems perform the write with a kernel thread (kjournald and
pdflush IIRC). I got a bit lost in the VFS-block devices interface so
I took the brute force of adding a xid field to struct page. The
performance loss is/was unmeasurable but still I don't like it :)

WRT your point that patching the kernel makes it insecure, IMHO it's
somewhat true but it all depends on the patch quality. Would you say
Openwall makes your box insecure? And AFAIK there's currently no way
to distinguish disk I/O between vservers to collect stats from

Best regards,
 Grzegorz Nosek
Vserver mailing list
Received on Fri Dec 16 14:57:21 2005

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