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Today's Topics:
1. Re: [EXTERNAL] Re: extremely slow DHCPD startup time (perl-list)
2. Re: extremely slow DHCPD startup time (Kenneth Porter)
----------------------------------------------------------------------
Message: 1
Date: Fri, 5 Aug 2022 09:45:07 -0400 (EDT)
From: perl-list <[email protected]>
To: Users of ISC DHCP <[email protected]>
Subject: Re: [EXTERNAL] Re: extremely slow DHCPD startup time
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=utf-8
This wouldn't happen to be on a virtual would it?
In my somewhat limited experience (only a couple high traffic DHCP servers in
virtuals - many on single SSD storage systems), I/O is a problem for DHCP
servers installed in virtual infrastructure (no matter what sort of storage you
have on the back end). A single CPU - multi core Xeon 1U system with a single
SSD and 16GB RAM will run circles around virtuals for ISC DHCP in the I/O
department. No idea why.
----- Original Message -----
> From: "Shane Merritt" <[email protected]>
> To: "Users of ISC DHCP" <[email protected]>
> Sent: Thursday, August 4, 2022 4:18:04 PM
> Subject: Re: [EXTERNAL] Re: extremely slow DHCPD startup time
> The server disks are already SSD. The total max available lease space
> according
> to dhcpd-pools is 283,751. I did a restart on one of the pair earlier and the
> time was about 10 minutes, but activity is low at the moment since fall
> semester hasn?t begun.
> Shane Merritt
> Office of Information Technology
> The University of Alabama
> [email protected]
> From: dhcp-users <[email protected]> on behalf of Sten Carlsen
> <[email protected]>
> Date: Thursday, August 4, 2022 at 2:54 PM
> To: Users of ISC DHCP <[email protected]>
> Subject: [EXTERNAL] Re: extremely slow DHCPD startup time
>> On 4 Aug 2022, at 21.05, Greg Sloop < [ mailto:[email protected] |
>> [email protected]
>> ] > < [ mailto:[email protected] | [email protected] ] > 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 < [ mailto:[email protected] |
>> [email protected] ] > 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
>>> [ mailto:[email protected] | [email protected] ]
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------------------------------
Message: 2
Date: Fri, 05 Aug 2022 09:55:15 -0700
From: Kenneth Porter <[email protected]>
To: Users of ISC DHCP <[email protected]>
Subject: Re: extremely slow DHCPD startup time
Message-ID: <61F9937FEEEAEB65706AFFFD@[192.168.69.69]>
Content-Type: text/plain; charset=us-ascii; format=flowed
--On Thursday, August 04, 2022 8:01 PM +0000 Shane Merritt
<[email protected]> wrote:
> The leases file on these boxes is around 200 megabytes.
I'd suggest trying Kea, the ISC DHCP server that's undergoing active
development. There's a tool to migrate the old configuration to the new
JSON format. Alas, there's no tool to migrate the lease file. That sounds
like a big obstacle for migrating big sites or testing the new software
against a big existing deployment database.
------------------------------
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End of dhcp-users Digest, Vol 166, Issue 3
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