On Mon, 2007-05-14 at 13:08 -0400, Scott McClanahan wrote: > On Mon, 2007-05-14 at 10:55 -0400, Ruslan Sivak wrote: > > Steve Huff wrote: > > > > > > On May 14, 2007, at 10:25 AM, Ruslan Sivak wrote: > > > > > >> Steve Huff wrote: > > >> > > >> If you set up a third box to be the shared storage, doesn't that now > > >> become the single point of failure? > > > > > > Short answer: maybe. :) > > > > > > Longer answer: If you set up your shared storage according to > > > upstream's guidelines, as described in the documentation > > > (http://mirror.centos.org/centos/4/docs/html/rh-cs-en-4/ch-hardware.html#TB-HARDWARE-NOSPOF), > > > then you provide at least two channels of communication between each > > > component in the cluster. In addition, you choose a platform for > > > shared storage that provides some redundancy of its own, whether it's > > > multi-controller HW RAID, or multiple storage nodes on a SAN, or what > > > have you. > > > > > > CS/GFS operates under the assumption that your shared storage is > > > fault-tolerant; its job is to make your services fault-tolerant. Is > > > the recommended "no single point of failure" configuration proof > > > against your data center burning down, or against a madman with an > > > axe? Unlikely. Will it allow you to host services in a way that is > > > considerably more robust and flexible than hosting them on a single > > > box? Yes. > > > > > > -Steve > > > > > > > I am currently running a redundant environment on windows by having 2 > > boxes with apache and having the data (images) be synced over > > automatically between servers using FRS (File Replication Service). > > This works well most of the time, except for when it breaks, at which > > point I need to resync the two servers, which usually takes days. > > > > I would like to set up something similar using linux. I don't have the > > budget for a SAN/NAS, and even having a third server as storage would > > probably not be worth it, although we can possibly go with this. The > > problem, is that it would be a single point of failure. > > > > Is there some service/filesystem in Linux that allows for the automatic > > replication of files to make a fault tolerant environment possible with > > only 2 servers? Basically whenever there is an update of a file on a > > certain file system (certain folder), the file gets synced over to > > another system. > > > > Russ The is clustering include in CentOS-5 ... see the guides for using C5 Clustering here: http://www.centos.org/docs/5/ > DRBD and Heartbeat seem pretty solid together for cheap affective high > availability. We've been using them for our production FTP servers > which handle hundreds of thousands transactions a day both > uploading/downloading. We fail over between the two every 6 months and > haven't had any problems on CentOS 4.3, they've actually been up for > several hundred days now. There is actually a yumgroup named > drbd-heartbeat in the CentOS extras repository but I don't see that it > is available in CentOS 5.0. Does anyone know if these packages will be > available in any of the CentOS 5.0 yum repositories? There is a testing DRBD / Heartbeat for CentOS-5 in the testing repository: http://dev.centos.org/centos/5/ Thanks, Johnny Hughes
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