high performance open source DHCP solution?
The free DHCP solution, ISC, seems to be having scaling issues (i.e. handling only about 200 DHCPDISCOVER and 20 DHCPRENEW requests), and I was wondering if anyone had any open source suggestions of solutions that could scale much better? (Ideally, I could find a free version of a solution like Nominum, but I know that's asking for much.) Anyone have any suggestions? -- Also on LinkedIn? Feel free to connect if you too are an open networker: scubacuda@gmail.com
On Tue, Jul 19, 2011 at 9:21 PM, Rogelio <scubacuda@gmail.com> wrote:
The free DHCP solution, ISC, seems to be having scaling issues (i.e. handling only about 200 DHCPDISCOVER and 20 DHCPRENEW requests), and I was wondering if anyone had any open source suggestions of solutions that could scale much better?
Where do you get that ISC DHCPD only handles 200 DHCPDISCOVER / 20 DHCPRENEW requests? That doesn't sound right. So I wonder what are you measuring? Is this a number of answers per second your implementation of ISC DHCPD is providing successfully? There are architectural facts about any environment besides what software is performing the DHCP task. How many I/Os + fsync()'s per second can this DHCP server handle that does only 20 renews? -- -JH
220-ish per second sounds roughly like a 1-disk (or 2 mirrored disk) IOPS problem, personally... But any number of other things could be affecting it. The number should be thousands if your disk / filesytem RAM cache / server configuration aren't inadequate... On Tue, Jul 19, 2011 at 8:54 PM, Jimmy Hess <mysidia@gmail.com> wrote:
On Tue, Jul 19, 2011 at 9:21 PM, Rogelio <scubacuda@gmail.com> wrote:
The free DHCP solution, ISC, seems to be having scaling issues (i.e. handling only about 200 DHCPDISCOVER and 20 DHCPRENEW requests), and I was wondering if anyone had any open source suggestions of solutions that could scale much better?
Where do you get that ISC DHCPD only handles 200 DHCPDISCOVER / 20 DHCPRENEW requests? That doesn't sound right. So I wonder what are you measuring?
Is this a number of answers per second your implementation of ISC DHCPD is providing successfully? There are architectural facts about any environment besides what software is performing the DHCP task.
How many I/Os + fsync()'s per second can this DHCP server handle that does only 20 renews?
-- -JH
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We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second. On Tue, Jul 19, 2011 at 11:08 PM, George Herbert <george.herbert@gmail.com>wrote:
220-ish per second sounds roughly like a 1-disk (or 2 mirrored disk) IOPS problem, personally...
But any number of other things could be affecting it.
The number should be thousands if your disk / filesytem RAM cache / server configuration aren't inadequate...
On Tue, Jul 19, 2011 at 8:54 PM, Jimmy Hess <mysidia@gmail.com> wrote:
On Tue, Jul 19, 2011 at 9:21 PM, Rogelio <scubacuda@gmail.com> wrote:
The free DHCP solution, ISC, seems to be having scaling issues (i.e. handling only about 200 DHCPDISCOVER and 20 DHCPRENEW requests), and I was wondering if anyone had any open source suggestions of solutions that could scale much better?
Where do you get that ISC DHCPD only handles 200 DHCPDISCOVER / 20 DHCPRENEW requests? That doesn't sound right. So I wonder what are you measuring?
Is this a number of answers per second your implementation of ISC DHCPD is providing successfully? There are architectural facts about any environment besides what software is performing the DHCP task.
How many I/Os + fsync()'s per second can this DHCP server handle that does only 20 renews?
-- -JH
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-- -george william herbert george.herbert@gmail.com
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On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton <ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second.
Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database. I do not recommend use of a RAMDISK; it's safer to bend the rule than break it entirely; a safer way is probably to use a storage system on a battery-backed NVRAM cache that you configure to ignore SYNC() and lie to the DHCP server application, allowing the storage system to aggregate the I/O. Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle. As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof. -- -JH
We've recently setup ISC DHCPd with failover for lease information, and LDAP as a configuration source (mostly because of our need for dynamically adding dhcp reservations for cable modems, etc) -- we don't have any performance issues thus far, but I'd imagine in a failover environment, it might be safe to consider a ramdisk for leases. Obvoiusly breaks RFC2131, but... Walter Keen Network Engineer Rainier Connect (P) 360-832-4024 (C) 253-302-0194 On 07/20/2011 03:28 PM, Jimmy Hess wrote:
On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton<ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second. Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database.
I do not recommend use of a RAMDISK; it's safer to bend the rule than break it entirely; a safer way is probably to use a storage system on a battery-backed NVRAM cache that you configure to ignore SYNC() and lie to the DHCP server application, allowing the storage system to aggregate the I/O.
Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle.
As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof.
-- -JH
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On Jul 20, 2011, at 3:37 PM, Walter Keen wrote:
We've recently setup ISC DHCPd with failover for lease information, and LDAP as a configuration source (mostly because of our need for dynamically adding dhcp reservations for cable modems, etc) -- we don't have any performance issues thus far, but I'd imagine in a failover environment, it might be safe to consider a ramdisk for leases. Obvoiusly breaks RFC2131, but...
Use an ssd, all the cool kids with monolithic databases and tpc-c style workloads are doing it and since your storage requirements are negligible it ought to be fairly cheap. http://www.intel.com/design/flash/nand/extreme/index.htm Bandwidth Sustained sequential read: up to 250 MB/s Sustained sequential write: up to 170 MB/s Read latency 75 microseconds I/O Per Second (IOPS) Random 4KB Reads: >35,000 IOPS Random 4KB Writes: >3,300 IOP and that's for just one disk.
Walter Keen Network Engineer Rainier Connect
(P) 360-832-4024 (C) 253-302-0194
On 07/20/2011 03:28 PM, Jimmy Hess wrote:
On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton<ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second. Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database.
I do not recommend use of a RAMDISK; it's safer to bend the rule than break it entirely; a safer way is probably to use a storage system on a battery-backed NVRAM cache that you configure to ignore SYNC() and lie to the DHCP server application, allowing the storage system to aggregate the I/O.
Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle.
As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof.
-- -JH
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Good luck buying X25-Es; they're out of production and all gone from supply chain. Replacement 710 and 720 models are ETA in late August at the moment. Micron has some large-cap SLC drives in the chain for September/October/ish timeframes. Ramdisk with rsync or rdiffbackup to spinning storage will do just fine. -george On Wed, Jul 20, 2011 at 4:01 PM, Joel Jaeggli <joelja@bogus.com> wrote:
On Jul 20, 2011, at 3:37 PM, Walter Keen wrote:
We've recently setup ISC DHCPd with failover for lease information, and LDAP as a configuration source (mostly because of our need for dynamically adding dhcp reservations for cable modems, etc) -- we don't have any performance issues thus far, but I'd imagine in a failover environment, it might be safe to consider a ramdisk for leases. Obvoiusly breaks RFC2131, but...
Use an ssd, all the cool kids with monolithic databases and tpc-c style workloads are doing it and since your storage requirements are negligible it ought to be fairly cheap.
http://www.intel.com/design/flash/nand/extreme/index.htm
Bandwidth Sustained sequential read: up to 250 MB/s Sustained sequential write: up to 170 MB/s Read latency 75 microseconds I/O Per Second (IOPS) Random 4KB Reads: >35,000 IOPS Random 4KB Writes: >3,300 IOP
and that's for just one disk.
Walter Keen Network Engineer Rainier Connect
(P) 360-832-4024 (C) 253-302-0194
On 07/20/2011 03:28 PM, Jimmy Hess wrote:
On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton<ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second. Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database.
I do not recommend use of a RAMDISK; it's safer to bend the rule than break it entirely; a safer way is probably to use a storage system on a battery-backed NVRAM cache that you configure to ignore SYNC() and lie to the DHCP server application, allowing the storage system to aggregate the I/O.
Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle.
As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof.
-- -JH
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On Wed, Jul 20, 2011 at 05:17:55PM -0700, George Herbert wrote:
Micron has some large-cap SLC drives in the chain for September/October/ish timeframes.
Ramdisk with rsync or rdiffbackup to spinning storage will do just fine.
Or hybrid zfs pools. -- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE
If you're just fighting IOPS, another compromise might be using a ramdisk, and then committing that data to storage every x seconds. Yes, you might be breaking the RFC, but depending on what it's used for, you could probably commit every 3-5 seconds without much penalty and limit your data loss potential on server failure. Or as others have said... some sort of SSD/cache solution. On Thu, Jul 21, 2011 at 12:41 AM, Eugen Leitl <eugen@leitl.org> wrote:
On Wed, Jul 20, 2011 at 05:17:55PM -0700, George Herbert wrote:
Micron has some large-cap SLC drives in the chain for September/October/ish timeframes.
Ramdisk with rsync or rdiffbackup to spinning storage will do just fine.
Or hybrid zfs pools.
-- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE
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* PC:
If you're just fighting IOPS, another compromise might be using a ramdisk, and then committing that data to storage every x seconds.
In this case, it's more straightforward to remove the fsync call from dhcpd. -- Florian Weimer <fweimer@bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
On Thu, Jul 21, 2011 at 2:41 AM, Eugen Leitl <eugen@leitl.org> wrote:
On Wed, Jul 20, 2011 at 05:17:55PM -0700, George Herbert wrote:
Micron has some large-cap SLC drives in the chain for September/October/ish timeframes.
Ramdisk with rsync or rdiffbackup to spinning storage will do just fine.
Or hybrid zfs pools.
+1
I should have given more information, we do ramdisk with rsync backups and have been running this way for over 2 years without any issues/lost leases. Nick Colton Allo Communications On Thu, Jul 21, 2011 at 9:03 AM, Charles Morris <cmorris@cs.odu.edu> wrote:
On Thu, Jul 21, 2011 at 2:41 AM, Eugen Leitl <eugen@leitl.org> wrote:
On Wed, Jul 20, 2011 at 05:17:55PM -0700, George Herbert wrote:
Micron has some large-cap SLC drives in the chain for September/October/ish timeframes.
Ramdisk with rsync or rdiffbackup to spinning storage will do just fine.
Or hybrid zfs pools.
+1
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----- Original Message -----
From: "Jimmy Hess" <mysidia@gmail.com>
Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle.
As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof.
I think a lot of this depends on the target audience of your server. It sounds like he's in a commercial WAN environment, which of course is what those rules were written for. But I can't tell you how many service calls I have to take because of address conflicts on home LANs behind consumer routers... which don't generally cache the assignments at all, IME. Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com Designer The Things I Think RFC 2100 Ashworth & Associates http://baylink.pitas.com 2000 Land Rover DII St Petersburg FL USA http://photo.imageinc.us +1 727 647 1274
In message <21226672.1947.1311207580967.JavaMail.root@benjamin.baylink.com>, Jay Ashworth writes:
----- Original Message -----
From: "Jimmy Hess" <mysidia@gmail.com>
Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle.
As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof.
I think a lot of this depends on the target audience of your server.
It sounds like he's in a commercial WAN environment, which of course is what those rules were written for. But I can't tell you how many service calls I have to take because of address conflicts on home LANs behind consumer routers... which don't generally cache the assignments at all, IME.
What I hate is my cable provider re-numbering without winding down the lease time first. Waking up in the morning to a lease that say its still got 18+ hours to go and no net shouldn't happen. If the DHCP server has said the address is good for 24 hours it should be good for 24 hours. I know first level support will say to reboot, which forces a renew which fails, but one shouldn't have to reboot for a renumber event. Run the old and new spaces in parallel for 24 hours. Mark -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@isc.org
SSDs can be a good alternative these days as well. Some of them have gotten to be quite fast. Sure, you'll have to replace them more often than spinning media, but, the write times can be quite a bit better. Owen On Jul 20, 2011, at 3:28 PM, Jimmy Hess wrote:
On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton <ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second.
Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database.
I do not recommend use of a RAMDISK; it's safer to bend the rule than break it entirely; a safer way is probably to use a storage system on a battery-backed NVRAM cache that you configure to ignore SYNC() and lie to the DHCP server application, allowing the storage system to aggregate the I/O.
Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle.
As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof.
-- -JH
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On Jul 20, 2011, at 6:25 PM, Owen DeLong wrote:
SSDs can be a good alternative these days as well. Some of them have gotten to be quite fast. Sure, you'll have to replace them more often than spinning media, but,
Actually the the scale of writes associated with this application is unlikely to significantly impact the service life of an SLC nand ssd with a solid block shadowing/wear leveling implementation. back in 2007 I was convinced that we could improve on the reliability of our network appliances with industrial 2.5" sata and enterprise sas disks, and the situation has only improved since.
the write times can be quite a bit better.
like orders of magnitude.
Owen
On Jul 20, 2011, at 3:28 PM, Jimmy Hess wrote:
On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton <ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second.
Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database.
I do not recommend use of a RAMDISK; it's safer to bend the rule than break it entirely; a safer way is probably to use a storage system on a battery-backed NVRAM cache that you configure to ignore SYNC() and lie to the DHCP server application, allowing the storage system to aggregate the I/O.
Of course, committing to a RAMDISK tricks the DHCP server software. The danger is that if your DHCP server suffers an untimely reboot, you will have no transactionally safe record of the leases issued, when the replacement comes up, or the DHCP server completes its reboot cycle.
As a result, you can generate conflicting IP address assignments, unless you: (a) Have an extremely short max lease duration (which can increase DHCP server load), or (b) Have a policy of pinging before assigning an IP, which limits DHCP server performance and is not fool proof.
-- -JH
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In article <CAAAwwbUDj4yGudeVRohAPywj=39ZjMApt0KYJw8Wa2sZhb9qcg@mail.gmail.com> you write:
On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton <ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second.
Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database.
Well, that's easily fixed (if the architecture of the server allows it): just queue up but don't send out the replies, then every 10ms sync the changes to the filesystem and then send out the replies. "fsync batching". Perhaps someone should suggest this to the ISC DHCPD developers. Mike.
In a message written on Fri, Jul 22, 2011 at 09:23:58PM +0200, Miquel van Smoorenburg wrote:
Perhaps someone should suggest this to the ISC DHCPD developers.
./configure --enable-delayed-ack Note, I've never used it, but it does what you describe. -- Leo Bicknell - bicknell@ufp.org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/
* Jimmy Hess:
On Wed, Jul 20, 2011 at 9:31 AM, Nick Colton <ncolton@allophone.net> wrote:
We were seeing similar issues with low leases, moved the dhcpd.leases file to a ramdisk and went from ~200 leases per second to something like 8,000 leases per second.
Yes, blame RFC2131's requirement that a DHCP server is to ensure that any lease is committed to persistent storage, strictly before a DHCP server is allowed to send the response to the request; a fully compliant DHCP server with sufficient traffic is bound by the disk I/O rate of underlying storage backing its database.
Come on, group commits are not that difficult to implement. With them, you should be able to obtain 8 kHZ leases on a single spindle (assuming the per-client data is just a few hundred bytes), without violating the RFC requirement. -- Florian Weimer <fweimer@bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99
hey,
The free DHCP solution, ISC, seems to be having scaling issues (i.e. handling only about 200 DHCPDISCOVER and 20 DHCPRENEW requests), and I was wondering if anyone had any open source suggestions of solutions that could scale much better?
You are doing something wrong: * turn off ping-check * use proper raid controller with battery backup (because isc dhcpd does fsync every time it writes to dhcpd.leases) * ... * profit -- tarko
participants (16)
-
Charles Morris -
Eugen Leitl -
Florian Weimer -
George Herbert -
Jay Ashworth -
Jimmy Hess -
Joel Jaeggli -
Leo Bicknell -
Mark Andrews -
Miquel van Smoorenburg -
Nick Colton -
Owen DeLong -
PC -
Rogelio -
Tarko Tikan -
Walter Keen