High availabiltiy improvement suggestions

[Dhaval Patel <dh...@yahoo.com>]

Hello all,

   One of my friend is looking a way to improve availability of his web-app which is deployed on
tomcat 5.0.28. He has following configuration:

Hardware: Dual Xeon 3.0 GHz, 73 GB 10K SCSI HDD, 2 GB RAM, Gigabit NIC
Software: SuSE Linux 10, JDK 1.5, Tomcat 5.0.28 (Default install)

   His web-app has about 2000 users and his company is expecting load of 10,000 more so say about
12,000 users. Currently tomcat is handling all users flawlessly. No problem whom-so-ever. Based
upon my knowledge, Tomcat is capable of handing more users then 12000. So absolutely NO need to
switch application server. He and I both have 100% trust in Tomcat and we are NOT going to switch
to any other application server.

   Now he discussed few things with me about providing high availability (and may be high
throughput). So in brief, we are looking at solution that provides high availability. 

   My questions are :

1) Do you know of any hardware/software configuration to increase high availability?
2) Does clustering helps in this situation? If yes, any reference on how to implement that? (I
dont mind reading esp. when it is new to me)
3) Does Apache play any role in this improvement scenario?
4) He wants configuration like, if one server dies for any reason, second identical server should
able to pick up requests and serve it. He does not mind adding hardware. How to do that?
5) Do you think load balancing may help? I mean server is pretty powerful and my friend does not
mind improving hardware. 12000 is not a big number. 

   Thank you all for reading above. Let me know your all suggestions.

Regards,
Dhaval

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Re: High availabiltiy improvement suggestions

[David Rees <dr...@gmail.com>]

On 3/15/06, Dhaval Patel <dh...@yahoo.com> wrote:
> 1) Do you know of any hardware/software configuration to increase high availability?

One way is to load-balance Tomcat instances behind Apache using mod_jk
and sticky-sessions. You can also use a hardware load balancer as
well. There are a number of options here which will work.

> 2) Does clustering helps in this situation? If yes, any reference on how to implement
> that? (I dont mind reading esp. when it is new to me)

Clustering Tomcat (see the docs) will allow you to move users from a
failed Tomcat instance to another without losing the user's session
state.

> 3) Does Apache play any role in this improvement scenario?

See above.

> 4) He wants configuration like, if one server dies for any reason, second identical server
> should able to pick up requests and serve it. He does not mind adding hardware. How to
> do that?

See above.

> 5) Do you think load balancing may help? I mean server is pretty powerful and my friend
> does not mind improving hardware. 12000 is not a big number.

You may be able to serve that load easily on your existing hardware,
or you may not be able to come close. It depends on the type of load
your app generates. You should be able to estimate how much more load
another 10k users will generate based on your existing load of 2k
users and go from there.

-Dave

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