Re: high performance, highly available web clusters
On Thu, 20 May 2004 15:48, David Wilk <firstname.lastname@example.org> wrote:
> The cluster is comprised of a load-balancer, several web servers
> connected to a redundant pair of NFS servers and a redundant pair of
> MySQL servers. The current bottle-neck is, of course, the NFS servers.
> However, the entire thing needs an increase in capacity by several
The first thing I would do in such a situation is remove the redundant NFS
servers. I have found the NFS client code in Linux to be quite fragile and
wouldn't be surprised if a cluster fail-over killed all the NFS clients (a
problem I often had in Solaris 2.6).
> However, for alot less money, one could simply do away with the file
> server entirely. Since this is static content, one could keep these
> files locally on the webservers and push the content out from a central
> server via rsync. I figure a pair of redundant internal web server
> 'staging servers' could be used for content update. Once tested, the
> update could be pushed to the production servers with a script using
> rsync and ssh. Each server, would of course, require fast and redundant
> disk subsystems.
Yes, that's a good option. I designed something similar for an ISP I used to
work for, never got around to implementing it though. My idea was to have a
cron job watch the FTP logs to launch rsync. That way rsync would only try
to copy the files that were most recently updated. There would be a daily
rsync cron job to cover for any problems in launching rsync from ftpd.
With local disks you get much more bandwidth (even a Gig-E link can't compare
with a local disk), better reliability, and you can use the kernel-httpd if
you need even better performance for static content. Finally such a design
allows you to have a virtually unlimited number of web servers.
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