extremely slow DHCPD startup time

[Sten Carlsen]

> On 4 Aug 2022, at 21.05, Greg Sloop <gregs at sloop.net> <gregs at sloop.net> wrote:
> 
> I'm sure others will have some useful suggestions - but I do know that improving disk I/O can seriously improve performance.
> I'm not sure if that will improve restart/start/reload times.
> 
> It would be pretty easy to test though, say swapping for an SSD/Nvme.
> (Or if you like living dangerously, putting the disk in RAM.)
> 
> 
> 
> On Thu, Aug 4, 2022 at 12:02 PM Shane Merritt <smerritt at ua.edu <mailto:smerritt at ua.edu>> wrote:
> I have a failover pair of DHCP servers running 4.4.2-P1 that handle a DHCP for a very large wireless network (>75k devices active at any time). The leases file on these boxes is around 200 megabytes.  The problem I am having is when I need to make a change and restart, DHCPD takes over 25 minutes to start giving out addresses.  I assume this is due to the large lease file.  I see that there are tons of leases in the file that are “binding state free” that in some cases are months old.  Are there any suggestions to improve this situation?
> 

AFAIK the server will fill its internal tables with every possible lease, most of them empty or marked free. I could be wrong about this.

So the question is how large your net blocks are?

If you e.g. have a /8 address space, that would amount to the server having to populate 2^24 (16 mill) entries in its internal table and do what ever processing etc it does for each entry. This may take time.

>  
> 
>  
> 
> Shane Merritt
> 
> Office of Information Technology 
> The University of Alabama
> smerritt at ua.edu <mailto:smerritt at ua.edu>
>          
> 
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