Optimising rndc reload times on a slave server with 50,000 zones

[Doug Barton]

On 02/26/2011 18:56, Dennis Perisa wrote:
> Hi folks,
>
> I'm looking for suggestions to substantially improve reload times on a
> slave that is serving 50,000 zones (mostly customer zones).
>
> 'rndc reload' is being executed on the slave every 15 minutes.

Yeah, don't do that. :)  Is this being done to handle updates to 
customer zones? If so, you're much better off to reload them 
individually (rndc reload zonename), or better yet use dynamic updates. 
If you're doing this for other reasons you need to expand.

> Due to
> the large number of zones to trawl through, the reload process is
> causing intermittent outages and/or significant delays to zone transfers.

Familiar problem.

> Here are some ideas I have:
> - use rndc reconfig instead

This sounds like you're trying to handle _adding_ new customer zones. In 
that case, yes you're much better off with reconfig.

> - separate zone files into separate dirs to improve O/S performance
> (currently, all zone files are in a single dir)

Depending on your OS this can help quite a bit. 10k files in one 
directory is the point where you can start to see problems, so 50k is 
likely well past this point. I had a structure with one level based on 
the first character of the domain, and the next level based on the first 
2 characters. That way you should be able to keep all the directories 
down to less than 5k files (due to uneven distribution of first 
characters in domain names).

> Are these viable options?  Any other thoughts/suggestions?

I did all 3 of these things in the past to handle over 600,000 zones, so 
you're definitely on the right track.

> This is expected to be a short-term fix while we consider brute force
> approach of throwing more cpu/mem/IO at this.

Depending on how much you plan to grow going forward you probably 
shouldn't consider these short-term steps.


hth,

Doug

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