linux-kernel - Re: inotify limits - thousands (tens of thousands?) of watches

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Date:	Wed, 20 May 2009 12:04:23 +0200
From:	Matthias Kaehlcke <matthias@...hlcke.net>
To:	Marcin Krol <mrkafk@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: inotify limits - thousands (tens of thousands?) of watches

El Wed, May 20, 2009 at 11:26:57AM +0200 Marcin Krol ha dit:

> First, apols for using up bandwidth, but I honestly found no other place  
> where I can ask about this (and get meaningful reply).
>
> I'm not a kernel programmer, but I want to develop a program that would  
> watch modifications in *all* user directories on a busy server using  
> inotify.
>
> This is for high-availability purposes - events would be collected and  
> once every several minutes changed dirs would be rsync'ed to failover  
> server or smth like that would be done.
>
> As inotify watches particular directory and not its subdirs, I would  
> have to watch all directories.
>
> This means I would have to create thousands or even tens of thousands of  
> inotify watches.
>
> So my questions are:
>
> 1. is it safe? that is, will it not lock the kernel up, or cause  
> excessive memory consumption?
>
> 2. is it economic in terms of CPU time and RAM? I have no idea how to  
> even measure such a thing happening in the kernel..

i can't answer your question whether inotify scales or not, but maybe
DRBD (http://en.wikipedia.org/wiki/DRBD) could be an alternative
approach for your problem

-- 
Matthias Kaehlcke
Embedded Linux Engineer
Barcelona

    Me lo contaron y lo olvidé, lo vi y lo entendí, lo hice y lo aprendí
                              (Confucio)
                                                                 .''`.
    using free software / Debian GNU/Linux | http://debian.org  : :'  :
                                                                `. `'`
gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4                  `-
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