> -----Original Message-----
> From: centos-bounces@xxxxxxxxxx
> [mailto:centos-bounces@xxxxxxxxxx] On Behalf Of Ruslan Sivak
> Sent: Monday, May 14, 2007 10:56 AM
> To: CentOS mailing list
> Subject: Re: HA with CentOS
>
> 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-har
> dware.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
You can check out DRBD, it does block-level replication of data.
-Ross
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