From owner-freebsd-questions@FreeBSD.ORG Mon Nov 17 19:22:30 2008 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 1DB7D1065679 for ; Mon, 17 Nov 2008 19:22:30 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout016.mac.com (asmtpout016.mac.com [17.148.16.91]) by mx1.freebsd.org (Postfix) with ESMTP id 090888FC20 for ; Mon, 17 Nov 2008 19:22:30 +0000 (UTC) (envelope-from cswiger@mac.com) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Received: from cswiger1.apple.com ([17.227.140.124]) by asmtp016.mac.com (Sun Java(tm) System Messaging Server 6.3-7.03 (built Aug 7 2008; 32bit)) with ESMTPSA id <0KAH00LSYSHGU590@asmtp016.mac.com> for questions@freebsd.org; Mon, 17 Nov 2008 11:22:29 -0800 (PST) Message-id: <5C9AC885-CFC2-4A35-A21E-CEAFB64694A2@mac.com> From: Chuck Swiger To: Alex Kirk In-reply-to: <20081117105714.19994onozp83obs4@mail.schnarff.com> Date: Mon, 17 Nov 2008 11:22:28 -0800 References: <20081117105714.19994onozp83obs4@mail.schnarff.com> X-Mailer: Apple Mail (2.929.2) Cc: questions@freebsd.org Subject: Re: CARP-Like Solution With Machines On Different Networks? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 17 Nov 2008 19:22:30 -0000 On Nov 17, 2008, at 7:57 AM, Alex Kirk wrote: > After doing some research on the matter, it looks like CARP would be > a winning solution - but only if the backup system was on the same > network segment as the primary box. Given that there's no money to > colocate a second backup system at the same facility as the main > machine (and protection against failure at the colo facility is one > of the primary drivers for the failover setup), however, it looks > like CARP wouldn't be useful. If you can't or aren't willing to pay for a second machine, I doubt that any clustering solution is going to be workable for you, frankly. Most of the high-availability clusters I know about depend either on a multipath SAN or NAS setup to provide a common filestorage point for cluster members to synchronize with (the "quorum" drive for M$ clustered SQL server, similar for Sybase ASE cluster or Oracle Parallel Server [now Oracle RAC]), or require something like a hardware loadbalancer (Foundry ServerIron, NetScaler, etc) which acts to distribute transactions only onto the parts of the cluster which are up and working. > That said, are there any solutions which behave similarly to CARP > that I could use for a pair of machines connected solely via the > Internet? For now, I'd even be happy if there was some way to simply > do TCP port-level proxying, so to speak (i.e. connections come in to > a given machine, and are proxied to the main system if it's up, but > go to the backup box if not)? > > Thanks in advance for any advice you can provide. TCP level proxying is suitable for shared read-only distribution of traffic (ie, such as static web content going against a pool of webservers, all of which can serve any of the traffic coming their way). IPFW + natd can do this much via: -redirect_address localIP[,localIP[,...]] publicIP These forms of -redirect_port and -redirect_address are used to transparently offload network load on a single server and distribute the load across a pool of servers. This function is known as LSNAT (RFC 2391). For example, the argument tcp www1:http,www2:http,www3:http www:http means that incoming HTTP requests for host www will be trans- parently redirected to one of the www1, www2 or www3, where a host is selected simply on a round-robin basis, without regard to load on the net. ...but this paradigm simply won't work for content-aware traffic (ie, anything which has a per-user "session") and it definitely won't work for a database. MySQL clustering is a less expensive possibility than most of the vendors listed above (M$ SQLServer EE is $25K per CPU, Oracle RAC is $60K per CPU), but even so Sun wants to bill at $2500 per day for a week of consulting to set it up for you. Regards, -- -Chuck