What will bring my LAMP Server to its knees?

[atreyu]

Hi,

I've set up an old Dell (specs below) to be a LAMP server for a friend. He needs it to run a webserver (Apache) with a back-end database (MySQL) so that he can have his customers log in to a website hosted on it, fill out a small form (CGI/Perl/Javascript) and save the data, for later reports-running.

The system works fine, as I've set it up. But now he tells me that there will be 600+ users in a few months, and that number will double the next year, and quadruple by the fourth year, at which time it will level off. So naturally, I am concerned about running it out of my basement on an aging workstation. Its not like its Facebook or anything; a user will log in one time, do his thing, and probably never log in again. But when it first goes live for a new crop of users, I'm sure it will be hit heavy for a few weeks.

I've set up plenty of LAMP servers before, but always for internal use, or if external, just for fun. I am curious what people can tell me about user traffic and what I can expect. We are looking into having it hosted using his ISP service (or some other, GoDaddy, etc.), but frankly, I'm finding most VPS offerings to be priced a bit steep for what we need/want.

Here are the specs of the Dell:

Dimension 4600i
Intel Pentium 4 2.80GHz/HT
512MB 400MHz SDRAM
Seagate Barracuda ST2000DM001 2TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5"

I should mention that the server is running Fedora 17, but I will probably move it to CentOS 6 (for stability) before it goes live. I'm also thinking of replacing Apache with nginX, to take advantage of the purported superior concurrent connections capability. I'll also max out the physical RAM (4GB) on the box. I'm also considering an SSD to replace the spinning disk.

Thanks for reading~

[Irithori]

Ok, that machine is a bit on the weak side by todays standards.
Also 2400 users alone doesnt say much. All at once or evenly distributed over e.g. a day?
The latter should be no problem at all, even for your hardware.

So before replacing parts of the (established) software stack and/or hardware: Look at the numbers.
How many users are there right now, and more importantly: How many use the site concurrently?
How many apache childs are there, how much memory does each one take?
How long does it take to process one form in perl and mysql?

In short: Look at your graphing, benchmark it by crafting (heavy) requests.

[atreyu]

Ok, that machine is a bit on the weak side by todays standards.

Truly. Which means that if I could get away with it - oh, salutations, Linux!

Also 2400 users alone doesnt say much. All at once or evenly distributed over e.g. a day?

I think it would be very unlikely that there would ever be more than 30-40 connections at a time, at first. Then maybe a couple hundred simultaneous connections later on, but that's a guess.

So before replacing parts of the (established) software stack and/or hardware: Look at the numbers.
How many users are there right now, and more importantly: How many use the site concurrently?

right now it is still in beta mode with a small user base, I believe around 30 users, but none of them have started to actually use it yet. That is part of my problem: I don't have use cases yet, just theory.

How many apache childs are there, how much memory does each one take?

Do you mean the httpd binary processes themselves? There are currently 9 of them.

How long does it take to process one form in perl and mysql?

I haven't timed it yet, but if I had to guess, it is not more than a second to a couple seconds right now.

In short: Look at your graphing, benchmark it by crafting (heavy) requests.

Added to the to-do list.

Thanks.