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Safe number of applications (or DBs) on one server?

Safe number of applications (or DBs) on one server?

Safe number of applications (or DBs) on one server?

Modern hardware is perfectly capable of handling many applications, or components of applications (eg databases, web server components, application servers etc).

Without the use of high availability technologies such as clustering how many applications would you consider appropriate to run on one set of hardware?
I'd also include in this hosting apps running in VMs on one specific server, since if the physical box goes down, so do the VMs running on it.

I've posted this here, since I'm talking mainly about database applications (although I also have to consider some application services), but it could go elsewhere.

I've got to find space on the servers I run for two new applications that will likely be coming in by the end of this year, plus also discontinue three old boxes, two of which host live systems at present, and I'm wondering how many live systems it is safe to put on one box.

Before you ask - I've asked my boss for his opinion, but he doesn't care "as long as they work." He doesn't have a great deal of technical knowledge to understand how they work and why having 4 or 5 live systems running on one server isn't a brilliant idea when it comes to application uptime (although its great for saving electricity and rack space in the machine room over 1 separate box each).

Does anybody have any guidance they'd be prepared to share on how they work out what is safe?


RE: Safe number of applications (or DBs) on one server?


I would never claim to know enough to comment on how to determine what is workable in terms of the number of systems on one box. I'm sure that whatever theory you apply there are going to be so many variables in the equation the only way to be sure is either with a *lot* of past experience or simply giving it a try. I know that my company has underestimated the infrastructure resources required to run certain applications in the past on more than one occasion.

What I am pretty certain of is that we do not have any critical applications running more than two to a box (although some of our apps/databases are *huge*, both in terms of complexity and size, so this may not apply in your circumstances).


Please do not feed the trolls.....

RE: Safe number of applications (or DBs) on one server?

ONe thing to avoid is running any other kind of application on a database server. SQl server (and i suspect some of the other databases) will suck up all available memeory and not let it go. This will cause interference with other apps. WHile you can limit the memory for SQl Server, you will then affect database performance, so it's not a good idea usually. We can and do host multiple databases on one server. How many would depend on the database size and the frequency of the queries against it. If the databases need to talk to each other, it may be better for them to be on the same server.

"NOTHING is more important in a database than integrity." ESquared

RE: Safe number of applications (or DBs) on one server?


Current max number of live apps per server is 2; but unfortunately with the new things coming in and servers going out of use I will have to take at least one of them to running 3 apps.
Our production dbs range from 10Mb to about 10Gb in size.

I understand the need to only run what is necessary on a server, unfortunately some of our apps need application services running on the same box so we can't really have a dedicated database server for these boxes.

My main reason for asking this question was that one of the servers that is going (hosts 4 dbs for 2 apps, but one is shared), plus both of the new apps are nominally pencilled in for all going onto one box (currently unused).

I'll have a think about this and see whether I can put one of the DBs somewhere else.

Thank you both.


RE: Safe number of applications (or DBs) on one server?

You will need to allocate (maximum) resources to each of the applications to avoid the situation SQLSister mentioned - the DB sucking up all the available resources. Your databases are relatively small so everything might be able to coexist on one multi-processor server. Alot will also depend on your peak usage times, both online and batch.

The trouble with doing something right the first time is that nobody appreciates how difficult it was - Steven Wright

RE: Safe number of applications (or DBs) on one server?


Some of our systems are of the order of terabytes, so you may well get away with more than two per server.

I believe one of our techniques is to split each server into two VPARS - one for the application, one for the database. Physical resources are explicitly assigned to each VPAR to avoid one application/database hosing another's resources.

Ed Metcalfe.

Please do not feed the trolls.....

RE: Safe number of applications (or DBs) on one server?

Oh well, I'll ponder this further and see what I can come up with.  I didn't think it would be easy working out what should go where, and you have proved me right.

Thank you all for your comments.


RE: Safe number of applications (or DBs) on one server?

We don't allow apps to be on a SQL box - DBs only.  Ours are load balanced based on observed activity on the databases.  We've got a handful of boxes that average 5-6 active DBs each.  Then again we also have one humoungous system that gets a whole cluster to itself.  

So my answer is "it depends".  winky smile

It's never too early to begin preparing for International Talk Like a Pirate Day
"The software I buy sucks,  The software I write sucks.  It's time to give up and have a beer..." - Me

RE: Safe number of applications (or DBs) on one server?

There are some things that are so mission critical like your database that you may want in a separate box due to the traffic and your data model.  There is a push to make the application and the database seperate.  Sometimes it makes sense to put Development and productions systems on the same box.

There is often a purposeful push to have one server with the database and a separate server with the Application and sometimes a separate server with SQL inbetween them.

If you do not like my post feel free to point out your opinion or my errors.

RE: Safe number of applications (or DBs) on one server?

Well, I raised this with one of the IT back office guys today who runs our SAN and infrastructure services, giving details of what apps are on each server and the details of what is going and what's coming in soon.
His advice was basically the same as here, but I now have to "size" each application based on its server usage footprint - CPU usage, disk usage, network bandwidth usage etc then take it from there.


RE: Safe number of applications (or DBs) on one server?

Under some models you can use an oversized server and use VMWARE and make it appear to function like 3 separate servers with 3 separate operating systems.  I have not seen this at our location but it poses other problems all of its own.  When the server pricing for software and applications is based on number of processors it can be hard to determine in a virtual environment.

If you do not like my post feel free to point out your opinion or my errors.

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