nanog mailing list archives
Re: high performance open source DHCP solution?
From: George Herbert <george.herbert () gmail com>
Date: Wed, 20 Jul 2011 17:17:55 -0700
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 _____ NANOG mailing list NANOG () nanog org https://mailman.nanog.org/mailman/listinfo/nanog_____ NANOG mailing list NANOG () nanog org https://mailman.nanog.org/mailman/listinfo/nanog_____ NANOG mailing list NANOG () nanog org https://mailman.nanog.org/mailman/listinfo/nanog
-- -george william herbert george.herbert () gmail com _____ NANOG mailing list NANOG () nanog org https://mailman.nanog.org/mailman/listinfo/nanog
Current thread:
- high performance open source DHCP solution? Rogelio (Jul 19)
- Re: high performance open source DHCP solution? Jimmy Hess (Jul 19)
- Re: high performance open source DHCP solution? George Herbert (Jul 19)
- Re: high performance open source DHCP solution? Nick Colton (Jul 20)
- Re: high performance open source DHCP solution? Jimmy Hess (Jul 20)
- Re: high performance open source DHCP solution? Walter Keen (Jul 20)
- Re: high performance open source DHCP solution? Joel Jaeggli (Jul 20)
- Re: high performance open source DHCP solution? George Herbert (Jul 20)
- Re: high performance open source DHCP solution? Eugen Leitl (Jul 20)
- Re: high performance open source DHCP solution? PC (Jul 21)
- Re: high performance open source DHCP solution? Florian Weimer (Jul 25)
- Re: high performance open source DHCP solution? Charles Morris (Jul 21)
- Re: high performance open source DHCP solution? Nick Colton (Jul 21)
- Re: high performance open source DHCP solution? George Herbert (Jul 19)
- Re: high performance open source DHCP solution? Jimmy Hess (Jul 19)
- Re: high performance open source DHCP solution? Jay Ashworth (Jul 20)
- Re: high performance open source DHCP solution? Mark Andrews (Jul 20)
- Re: high performance open source DHCP solution? Owen DeLong (Jul 20)
- Re: high performance open source DHCP solution? Joel Jaeggli (Jul 20)
- Re: high performance open source DHCP solution? Miquel van Smoorenburg (Jul 22)