Re: recommendations for the 'one writer, many reader' problem?

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: recommendations for the 'one writer, many reader' problem?
From: Zachariah Mully <zmully@xxxxxxxxxxxxxx>
Date: 29 Nov 2001 12:25:25 -0500
On Thu, 2001-11-29 at 12:06, Joseph Mack wrote:
> Matthijs van der Klip wrote:
> > 
> > Hi,
> > 
> > Right now I'm using rsync to keep 4 lvs'ed webservers in sync with a
> > seperate upload server, but I'm afraid rsync won't last me long. Does
> > anyone have any recommendations to solve the 'one writer, many reader'
> > problem given the following facts?:
> > 
> > 1) A docroot of 5GB data, 275K files and growing...

        Since rsync doesn't look long for your system, what is the fs thrash?
How much is the docroot changing daily? If not a tremendous amount, then
you might want to look at simple NFS mounting the update server and
letting the webservers cache everything. In our setup, we do about 10-20
updates daily (40-50 static html pages, as well as 10-20 new images) to
our update server, which is then NFS mounted on the webservers. We've
found that Apache is pretty good at caching those static html pages and
images, so we're not seeing any excessive use of the NFS mounted
directories, in fact once apache gets the first couple requests for the
pages, it is loaded and kept in memory on the webserver.... It's not
until about 5 days later that I see these pages being accessed over NFS
(they're daily news updates, so their access rate trickles down after a
couple of days and apache eventually unloads the page from memory).
        This situation is, of course, drastically different for dynamic pages.
Be very interested to hear of your solution as I will soon be looking at
other methods of doing this. Perhaps a shared disk cluster? Ultra SCSI
should be plenty fast enough. Or as someone else mentioned, look at
shrinking your rsync window... I dunno what type of data you have to
sync, but on some of our systems some directories get updated by rsync
every 30sec-1min (probably not the best use of rsync, but it works!).


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