Are they upselling me, or am I really bumping up against the limits?

Greetings all - I run the technical side of a music-related forum on phpBB 3.0.5 on a VPS with 256 MB RAM burstable to 1 GB. We have 750K posts, with about 2000 users, of which 200 or so are active users. We generally average only 15-20 users on line at any time, and we might see 30 or 40 users on when there's some event happening, The only MOD on the board is a humanizer question on the registration screen, plus a bit of code to make sure only registered users can hit the search page. In other words, about as vanilla as you'd want to get.

We recently got what I'd call a nastygram from our hosting provider saying that we've been consistently bursting to over our "CPU limit". Now, I've heard of memory burst limits, but processor utilization limits? Taking a look at CPanel I see load averages of 0.73 0.66 and 0.46 right at the moment (with a brief jump up into the red at 1.12 five mins ago with 28 users on).

Nothing horrendous in terms of usage, and taking a look at PHPMyAdmin, MySQL looks like it's straight out of the box - no tuning whatsoever.

Given that this is a relatively small forum in the grand scheme of things, I'd find it hard to believe we're serving up all that much based on the stats and the performance (usually pretty good), and that we have that many long running queries or PHP scripts. It just doesn't add up, and I don't think the database is at the point where it needs partitioning (not that that would do any good without multiple disks to put things on).

Based on these numbers, your experience and gut check, what do you think? My gut check is that the VPS environment is highly unoptimized and that some changes which have impacted performance have been made (I can only say that we had about 2-3 weeks of horrendous performance back in September, which they claimed was our fault due to long running queries, but then these issues mysteriously vanished and the server has been running smoothly since). I'm not necessarily happy about doubling my monthly recurring charges to go to the next level of VPS service, but if the gut check here is that it's indicated, I'll bite the bullet.

Thanks in advance for your comments and insight.

 

Hey Vox,

I'm not expert, but of the information that you've provided, you didn't indicate that they (host) explicitly provided you support for their claims (e.g,. logs, reports) directly linking your site to the usage.

I'm not sure the cpanel info is really reporting for only your instance, maybe someone can shed light on that.

I have the same gut check as you though considering your instance of phpbb. But really, whenever there are such claims like that, to me the burden of proof is on them to show you that your site is overusing.

Good luck and report back, b/c I'm sure others will benefit from this.

 

Never heard of a CPU limit cap, but I've never had VPS. Perhaps that's something they do monitor?

As said above, I'd request a report of some type showing the usage since day 1 and see if it matches your events etc, and take it from there.

 

With 750,000 post, you should be on a high level virtual private server. I think the only reason why your not on a high end VPS or an entry level dedicated server is because you only have 200 active users and 15 - 20 people on the site at one time.

I wonder if your hitting a limit that prevents more people from logging into the site at one time?

My suggestion is to get upgraded to a good VPS with at least 768 megs of memory.

 

I don't think we're bumping up against anything that's preempting anyone from logging in - I've had as many as 77 users on simultaneously back when we were on a shared server and we weren't breathing hard at all.

Based on performance testing I've done at work 250 people hitting Enter or clicking at the same time shouldn't cause anything more than a momentary blip, but who knows how over-subscribed my hosting provider is on their VPS boxes?

Since I've posted the original post a couple of hours ago, I've averaged about 25 users online (didn't check post count though) and load hasn't gone above 0.46 on CPanel.

I suppose I can save the rant about at least getting a vmstat output out of CPanel or better logging in phpBB for another thread

Update - in terms of "active" users I've got 420 users with over 100 posts, 240 with over 500 posts each.

 

FWIW I have a smaller vB forum than you with around 1500 registered members, about 150 returning daily, and not much more than 50 or so on at the same time and I'm on a VPS with 1 GB of dedicated RAM burstable to 4 GB. I've never had any complaints from my host about hitting limits. I do monitor 'top' from time to time over ssh and don't see anything out of order as far as load and memory usage. I should note that there are also 3 smaller forums hosted on this server.

Some hosts (both shared and VPS) do limit CPU cycles and/or CPU time yours is probably one of them. See if you can tweak phpBB to use less resources or perhaps some MySQL and PHP tweaks are in order. Caching could be an option if you cannot afford to upgrade. If your host is managed they should be able to tweak and setup caching for you if you feel that's necessary.

If your in the market for a new VPS host, ServInt is awesome!

 

I keep hearing about ServInt's awesomeness, I hope one day to need that. : )

Thank you for sharing your stats!

 

Taking a look at the "top" output, I see the CPU utilization hovering between 6 and 7% over the last couple of hours, never higher. Never saw memory utilization above 128MB, and nothing oddball running and sucking CPU cycles. We've had about 25-30 users online pretty constantly since the original post. Didn't check how many posts have actually been made this afternoon, but on average we get 400-405 new posts/day. So far I haven't seen anything that indicates anything out of the ordinary, so I'm still not completely sold on the need for upgrading my VPS plan at this point.

 

How about when your cron jobs run? People often forget about that. vB has it's cron jobs as Scheduled Tasks those aren't really the ones that matter though don't forget your server has all kinds of crons; the stats software (awstats etc) is often the largest in terms of CPU & RAM utilization perhaps that is what's hitting the limit when it runs normally this is in the early morning hours?

If so, just disable it and use Google's Analytics for stats.

Other than that if top looks good your host may be trying to pull a fast one.

 

No cron jobs running - phpBB doesn't require any, and I have no mods or anything else running that requires them. I am toying with the idea of using OpenX ad server to rotate ads from forum sponsors, and that of course would require a maintenance cron job, but that's assuming I can sell some forum sponsorships :lol:

 

No CRON jobs? When are you making backups?



I called ServInt and they indicated that there are "slices to the pie" (cpu cycles) for them. I don't believe it would be possible to go over. I am not saying you should be switching hosts, I'm just confused how it is possible to go over on a vps.

I'm no expert at all though.


I really would not put up with a lot of grief from any one host before trying another one. I'm impressed you got 250 people to click 'Enter' at the same time! Sounds like something I would do.

 

I just run my backups manually a couple of nights a week. I know, I know....

The 250 people actually happened back around '97 or '98. Not enough budget for Mercury tools, but enough for a few deli trays

 

Do you run any type of control panel in your account apart from that forum?

 

Just CPanel - finally got SSH working yesterday so I can run top.

 

256MB of ram is extremely low, simply upgrading that to 512 should suffice since phpBB isn't exactly the most optimized script in the entire world. Especially on a cPanel/WHM server as its a pretty source hogging script.

Your total posts, and threads don't really factor much here, what matters is how many people are online at one time, this includes guests, spiders and members, so theoretically while you see 28 active users, you could have a much higher number thats causing the problem.

If you're really on a VPS you can optimize the services for mysql, php and apache to help you stay with the current 256MB. Optimizing MySQL itself, could save you a huge amount of head aches. (usually my.cnf file)

You can always switch hosts if you feel your current hosting company isn't providing you with a high level of service for the price your paying. FutureHosting, PowerVPS and ASmallOrange are 3 great providers for VPS's at decent prices.

 

Well, I just let top run overnight, and apart from some momentary blips of 12-15% CPU utilization (none of which lasted longer than one repeat) the server has been quite happily running at an average CPU utilization of just about 1.5%. We've actually had a bit higher usage last night than normal, with about 30-35 users on simultaneously for most of the evening and I didn't see anything like heavy memory use (the most top reported was 132MB in use) nor any sort of indication of the server being consistently heavily loaded. No complaints from the users about slowness (and believe me I get them....)

I will take a crack at optimizing MySQL, but given the relatively small size of the board I don't think it's going to buy me all that much memory or performance improvement at this point. I'm not completely sold that throwing more hardware at this is the right thing to do at this point.

BTW, I really appreciate all the great feedback.

 

As David said 256MB of RAM is pretty low. Are you running cPanel? As I understand it WHM/cPanel pretty much take up that 256 MB with it's overhead.

It's sort of like running XP on 256 MB of RAM. Sure you can do it but when you want to do more than 1 thing or have a couple of programs open everything starts swapping out and the system slows to a crawl.

WHM has it's own set of cron jobs, I still say that's where your hitting up against hard limits. Take a look at this: https://www.solarvps.com/forums/index.php?topic=330.0;wap2