What's a mirror site?

[mrfrogs]

What is a "mirror" site? and when do I need one?

[qball]

Simply a "mirror" is a duplicate of a website with web server capabilities. Thus, each server can serve the same site.

Mirroring is done to increase a site's bandwidth, thus performance.

Mirroring is good on end user performance, though replication issues now become an issue.

[mrfrogs]

Thanks for your reply. So if I have a site that now gets more than 6000 uniques/day and it starts to get slow, what I could do is just upload a duplicate of the site to another server and let my viewers know they can go to either version of the site, right? That way the original site would have less traffic and will speed up a little.

[dragonB]

yes..
but for many large scale websites it's a lot more complicated than that.
I can guratee that ebay has more than one server, but if you type www.ebay.com, you always get the same thing. :)

I don't know a lot about it, but there's usually a machine that sits on the edge of their network, that the domain name points to. This machine then redirects the requests to different servers, thus spreading it around, and one machine doesn't do all the work.
Now, like qball hinted at, this gets really problematic with replication, or making the actual copy of the websites..
For example ebay is always changing, so it's not just a matter of putting the same website on each webserver..

dragonb

p.s. for a website with 6000 hits a day, 1 server should be able to handle it. If not, it's probably a very weak machine, and it would be cheaper to upgrade to 1 nice server than have 2 and worry about mirroring.(servers have a VERY broad price range, btw. anywhere from the $5 linux machine I have hosting my family's website, up to well over 100K or even more)

[qball]

dragonB,

don't mix up load balancing with mirroring, see:

http://searchstorage.techtarget.com/sDefinition/0,,sid5_gci212579,00.html

Now I don't know exactly how ebay is architected, but it is probably good example of dynamic web/app server switching, not mirroring. Each IP request to www.ebay.com goes to probably one web server that will load balance across a slew of web servers (most likely) that merely post the 'starting html' with advertising. Now once a user clicks a link on the home page, all bets are off. Each link on that page could have it's own web/app/db server config, in fact clicking, "Dolls&Bears" brings you to, drum roll please:

http://pages.ebay.com/catindex/dolls.html?ssPageName=HDB01

Now, ebay is pretty good, as one can see by trying:

http://pages.ebay.com/