[CentOS] HA with CentOS
Johnny Hughes
mailing-lists at hughesjr.com
Tue May 15 21:31:06 UTC 2007
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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