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
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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?
_______________________________________________
Looks interesting. I will have to try them out once they're in the
stable repo. Looks as of DRBD-8.0.0, you can use it together with GFS
and run both nodes as primary. Would heartbeat still be needed? Can
heartbeat work with VM boxes?
Russ
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