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Today's Topics:
1. extremely slow DHCPD startup time (Shane Merritt)
2. Re: extremely slow DHCPD startup time
(Greg Sloop <gr...@sloop.net>)
3. Re: extremely slow DHCPD startup time (Sten Carlsen)
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Message: 1
Date: Thu, 4 Aug 2022 19:01:23 +0000
From: Shane Merritt <smerr...@ua.edu>
To: "dhcp-users@lists.isc.org" <dhcp-users@lists.isc.org>
Subject: extremely slow DHCPD startup time
Message-ID:
<ds0pr15mb5400427309929336f4e55544a6...@ds0pr15mb5400.namprd15.prod.outlook.com>
Content-Type: text/plain; charset="windows-1252"
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?
Shane Merritt
Office of Information Technology
The University of Alabama
smerr...@ua.edu
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Message: 2
Date: Thu, 4 Aug 2022 12:05:46 -0700
From: "Greg Sloop <gr...@sloop.net>" <gr...@sloop.net>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: extremely slow DHCPD startup time
Message-ID:
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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 <smerr...@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?
>
>
>
>
>
> Shane Merritt
>
> Office of Information Technology
> The University of Alabama
> smerr...@ua.edu
>
>
> --
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
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Message: 3
Date: Thu, 4 Aug 2022 21:54:18 +0200
From: Sten Carlsen <st...@s-carlsen.dk>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: extremely slow DHCPD startup time
Message-ID: <b799ce36-5457-415e-a35d-25f0bcd38...@s-carlsen.dk>
Content-Type: text/plain; charset="utf-8"
> On 4 Aug 2022, at 21.05, Greg Sloop <gr...@sloop.net> <gr...@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 <smerr...@ua.edu
> <mailto:smerr...@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
> smerr...@ua.edu <mailto:smerr...@ua.edu>
>
>
> --
> ISC funds the development of this software with paid support subscriptions.
> Contact us at https://www.isc.org/contact/ <https://www.isc.org/contact/> for
> more information.
>
> dhcp-users mailing list
> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
> https://lists.isc.org/mailman/listinfo/dhcp-users
> <https://lists.isc.org/mailman/listinfo/dhcp-users>
> --
> ISC funds the development of this software with paid support subscriptions.
> Contact us at https://www.isc.org/contact/ for more information.
>
> dhcp-users mailing list
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> https://lists.isc.org/mailman/listinfo/dhcp-users
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