Re: [cobalt-users] Load Balancing Cobalts ?

["Rodolfo J. Paiz" <rpaiz@xxxxxxxxxxxxxx>]

At 4/9/01 10:30 AM -0500, you wrote:
> Mirroring two RaQs seems to be an interesting challenge... especially for
> mail... considering MX only happens on a single IP address. What if user
> logs into server2 and mail is being delivered to server1?

This is a problem with mirroring, which I don't know how to solve. However, 
it is not a problem with clustering where both machines think and act as one.

> Web/ftp is relatively simple to make work. Where I work, we use round-robin
> in DNS to present hosts www1 and www2 as www and simply cron (or manually
> run) a script to copy web root from www1 to www2. We're moving these to
> multiple Win2k boxes and will use a NetScreen firewall to handle the load
> balancing.

Good luck. But note that round-robin DNS provides load-sharing... not 
balancing, and no fault-tolerance with it. If one of your hosts dies, then 
50% of users will get the site and the other 50% will not. And if one 
machine is more powerful than another, they will still get the same amount 
of queries.

> Another option for higher volume sites, point multiple systems back to a
> common NFS mounted NAS volume. This way you only have one place to
> store/edit data.

Yeah, this seems like a great thing to me. However, I keep bumping my head 
into one thing: what if my NAS motherboard dies? That's an OOPS on a cosmic 
scale... Also, aren't there ***MAJOR*** security problems with NFS? I know 
nothing about it myself, but have heard this "around." Someone care to 
comment on this?

> Then you only have to provide some method of presenting the
> multiple servers as a single address.

Clusters will do this. Check out Beowulf (don't know URL...) and RedHat's 
Piranha (included in RH7 and found on their site) for examples. I'm not 
sure how to apply this to Cobalt stuff, but I'd like to.

> I'm told Apache will scream when the server can simply
> hand out pages without needing to handle disk reads.

This I didn't even understand... can you say that in English?

Also, Dave, I'd appreciate it if you'd trim some of the fat from older 
messages when you post replies. It makes continuing the thread easier.


--
Rodolfo J. Paiz
rpaiz@xxxxxxxxxxxxxx