I got a website, will create many subsites under this one ( may be around 300). Can I place all these susbites under one application pool?
You can host several web sites in the same application pool, but you should understand that you're creating a dependency among the sites in the same application pool -- they'll run as part of the same process, and if you have to restart the application pool for any reason, it will affect all sites in that pool. In some cases, this might make sense for you, but you should probably review online documentation to be sure this is what you want to do.
Introduction to IIS 7 Architecture
Managing Application Pools in IIS 7
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In IIS 7, what is best practice? Should I create an application pool for each application, or should I share an application pool with as much application as possible?
Are there any performance drawbacks or security issues related to one of the options?
Each application pool is an instance of W3wp.exe, a worker process for that site or set of sites. By placing each application in a seperate app pool, you ensure that problems that could potentially cause problems within the app pool do not cause problems with other applications. There is obviously an overhead to operating like this in terms of resources.
So generally, for simple sites and blogs I usually put these in a shared app pool. For more intensive or important applications, I seperate into individual app pools. This is just a guide to how I operate.
I believe IIS7 now creates seperate app pools when you create a web site (not 100% though).
In theory it is better to put each site to its own pool. In practice it takes much more RAM than placing the sites to a single pool. So, on most servers you will see 10-100 pools only, even if there are 1000 sites.
Sharing Application pool is better than creating an application pool for each application for a fixed number of application
You can run as many application pools on your IIS 7 server as you need but this will affect server performance.On the other hand Application pools allow a set of Web applications to share one or more similarly configured worker processes but you should not share an application pool to a lot of application.Because This will affect your server performance too!
So in both way you have to be tactful.
I've been looking at application pools lately, specifically with ASP.NET applications in mind and I've been struggling to find any best practices for use of application pools.
Of course alot depends of the size and scale of your destined apps in regards to memory limits etc, but I was more specifically thinking along the following lines...
If developing relatively small .net apps which need to be deployed underneath an existing site, should I as a best practice be creating a new virtual directory and application pool for each app?
Or should I just run them underneath the sites already present app pool?
Secondly are there any limits to the amount of app pools you can run (realistically and again assuming small apps with memory limits auto-handled and not defined) on a standard web server?
With resilliance and optimisation in mind my initial thought is to create a new v dir and app pool per app under the parent site - I just wondered if anyone has any thoughts on best practice or links that may assist?
Cheers
For resilience, create a separate application pool for each application. That way if an event occurs in one application that causes the pool to stop, it is only THAT application affected, and not any others on your server.
This also helps in terms of security - the application pool controls the identity of the running application. You should only give just enough permissions for the application to run on the machine. If one application requires access to a specific folder on the server, that doesn't mean you should be giving the same access to all of your applications.
What exactly is an application pool? What is its purpose?
Application pools allow you to isolate your applications from one another, even if they are running on the same server. This way, if there is an error in one app, it won't take down other applications.
Additionally, applications pools allow you to separate different apps which require different levels of security.
Here's a good resource: IIS and ASP.NET: The Application Pool
I second the top voted answer, but feel like adding little more details here if anyone finds it useful.
short version:
IIS runs any website you configure in a process named w3wp.exe. IIS
Application pool is feature in IIS which allows each website or a part
of it to run under a corresponding w3wp.exe process. So you can run
100 websites all in a single w3wp.exe or 100 different w3wp.exe. E.g.
run 3 websites in same application pool(same w3wp.exe) to save memory
usage. ,run 2 different websites in two different application pools so
that each can run under separate user account(called application pool
identity). run a website in one application pool and a subsite
'website/app' under a different application pool.
Longer version:
Every website or a part of the website,you can run under an application pool.You can control some basic settings of the website using an application pool.
You would like the website to run under a different w3wp.exe process.Then create a new application pool and assign that to the website.
You would like to run the website and all it's code under a different user account(e.g under Admin privileges),you can run do that by changing Application Pool Identity.
You would like to run a particular application under .net framework 4.0 or 2.0.
You would like to make sure the website in 32 bit mode or have a scheduled recycle of the w3wp.exe process etc.All such things are controlled from iis application pool.
Basically, an application pool is a way to create compartments in a web server through process boundaries, and route sets of URLs to each of these compartments. See more info here: http://technet.microsoft.com/en-us/library/cc735247(WS.10).aspx
An application pool is a group of one or more URLs that are served by a worker process or set of worker processes. Any Web directory or virtual directory can be assigned to an application pool.
Every application within an application pool shares the same worker process.
Assume scenario where swimmers swim in swimming pool in the areas reserved for them.what happens if swimmers swim other than the areas reserved for them,the whole thing would become mess.similarly iis uses application pools to seperate one process from another.
IIS-Internet information Service is a web server used to host one or more web application .
Lets take any example here say Microsoft is maintaining web server and we are running our website abc.com (news content based)on this IIS.
Since, Microsoft is a big shot company it might take or also ready to host another website say xyz.com(ecommerce based).
Now web server is hosting i.e providing memory to run both websites on its single web server.Thus , here application pools come into picture .
abc.com has its own rules, business logic , data etc and same applies to xyz.com.
IIS provides two application pools (path) to run two websites in their own world (data) smoothly in a single webserver without affecting each ones matter (security, scalability).This is application pool in IIS.
So you can have any number of application pool depending upon on servers capacity
An application pool is a group of urls served by worker processors or set of worker processors.
There can exist any number of application pools.
In IIS it is possible to create more than one application pool.
An application in different application pool runs in different worker processors.
Advantage: If an error occurred in one application pool will not effect the applications running in another application pool.
An Application pool is a collection of applications which uses the same worker process of IIS (w3wp.exe). Primary concern of using Application pool is to isolate two different applications with different security concerns and also to avoid crashing of applications due to worker process death.
An application pool is a group of one or more URLs that are served by a worker process or set of worker processes. Application pools are used to separate sets of IIS worker processes that share the same configuration and application boundaries. Application pools are used to isolate our web application for better security, reliability, availability and performance, and they keep running without impacting each other.
Application pools are used to separate sets of IIS worker processes that share the same configuration and application boundaries.
Application pools used to isolate our web application for better security, reliability, and availability and performance and keep running without impacting each other . The worker process serves as the process boundary that separates each application pool so that when one worker process or application is having an issue or recycles, other applications or worker processes are not affected. One Application Pool can have multiple worker process Also.
Or we can simply say that, An application pool is a group of one or more URLs that are served by a worker process or set of worker processes. Any Web directory or virtual directory can be assigned to an application pool. So that one website cannot be affected by other, if u used separated application pool.
Source : Interviewwiz
An application pool is like a pond, if I create 2 application pools, first application pool has 100 fishes and another application pool has 200 fishes, here fish is like an application in application pool.
They are managed by worker processes. Best advantage is: if pond number-1 has bad water and cases all fish are effected then there is security of fish in pond number-2. Like this if any application pool is affected by any problem but there is not any effect of this problem in application pool 2 so security improves, and another benefit is that is you provide all the necessary authentication and rights to all applications in a single application pool.
An application pool is a group of one or more URLs that are served by a worker process or set of worker processes. Application pools are used to separate sets of IIS worker processes that share the same configuration and application boundaries.
Application pools are used to separate set of IIS worker processes that share the same configuration.
Application pools enable us to isolate our web application for better security, reliability, and availability
The application Pools element contains configuration settings for all application pools running on your IIS. An application pool defines a group of one or more worker processes, configured with common settings that serve requests to one or more applications that are assigned to that application pool.
Because application pools allow a set of Web applications to share one or more similarly configured worker processes, they provide a convenient way to isolate a set of Web applications from other Web applications on the server computer.
Process boundaries separate each worker process; therefore, application problems in one application pool do not affect Web sites or applications in other application pools. Application pools significantly increase both the reliability and manageability of your Web infrastructure.
application pool provides isolation for your application. and increase the availability of your application because each pool run in its own process so an error in one app won't cause other application pool. And we have shared pool that hosts several web applications running under it and dedicated pool that has single application running on it.
I've read recommendations that we should create separate application pools for each asp.net application on our Win2008 server.
We have about 20 apps that would be on the same server. I know this would create 20 separate worker processes which seems very wasteful.
Is it good practice to create separate application pools for each application?
Reposted from ServerFault, "Why add additional application pools in IIS?"
AppPools can run as different identities, so you can restrict permissions this way.
You can assign a different identity to each app pool so that when you run task manager, you know which w3wp.exe is which.
You can recycle/restart one app pool without affecting the sites that are running in different app pools.
If you have a website that has a memory leak or generally misbehaves, you can place it in an app pool so it doesn't affect the other web sites
If you have a website that is very CPU-intensive (like resizing photos, for instance), you can place it in its own app pool and throttle its CPU utilization
If you have multiple websites that each have their own SQL database, you can use active directory authentication instead of storing usernames/passwords in web.config.
Separating apps in pools is a good thing to do when there's a reason, and there are a number of good reasons listed above. There are, however, good reasons not to separate apps into different pools, too.
Apps using the same access, .NET version, etc. will run more efficiently in a single pool and be more easily maintained. Most annoyingly, IIS will kill idle app pools, requiring the pool be recreated on each use. If you isolate infrequently used apps you'll impose an unnecessary startup cost on users. Combining these apps into a single pool will make for happier users when they don't pay the startup cost, happier servers when they don't give memory to multiple processes and CPU slices for them, and happier admins when they have to manage fewer app pools.
I used to have 58 .Net websites and 17 old classic ASP websites on the same IIS7.5 server using separate app pools for each site. I noticed that the IIS compression started failing intermittently, causing the style sheets to be corrupted about 5% of the time. Looking at the task manager on the server, I could see that the server was approaching it's 4GB ram limit- each w3wp.exe process was taking anything up to 100 MB memory depending on how much traffic the site was getting. I then moved all the websites into just 2 application pools (one for .net 4 websites and one for the old classic ASP sites) and the total memory used after doing that dropped from 3.8GB to just under 2.8GB - saving me over 1GB memory space on the server. After the change (and leaving the server running for a couple of hours to get back to normal levels of traffic), the w3wp processes were using 300MB for all the .net websites websites and 20MB for the classic ASP websites. I could re-enable IIS compression again without a problem.
Using separate APP pools is a great idea for many of the reasons mentioned by the other posts above, but it also in my experience causes a much higher memory overhead if you are hosting a fair number of websites on the same server.
I guess it's a trade-off between hardware restrictions and security whether you want to use separate app pools. It's a good idea if you have the resources to do it.
yes, it is a good idea even for 20 applications.
Security. Different app pools running under different accounts.
Isolation. One crashing app won't take down other apps.
Memory (if you are running 32bit). Each app pool will have its own address space. Thus you can address much more memory than a maximum of approximately 2.7GB of usable space for 1 process.
You may choose to periodically restart one not-so-well behaving app without affecting other applications.
If your apps are stable and don't use much memory, then I would say that it's fine to put them in the same app pool. App Pools give you isolation between your applications.
One main reason I consider when creating app pools is the process management. There are other reasons such as security etc.
When an IIS-hosted application crashes it takes down its host process as well. In previous versions of IIS this meant all web activity crashed together. With app pools you can isolate your applications from one another. If one has a memory leak and keeps crashing your other apps will continue to function.
The main benefit of creating different application pools is that you can provide each pool with other credentials. Your 20 applications may communicate with 20 different databases that all need another login. The best practice then is to run each application using a different service account.
I wouldn't worry too much about performance. Most time will probably be spent inside each web application, no matter what process each application is in.
This really depends on the applications, your security model, and how much you trust the applications.
Here are a few things that I always tell people to consider when working with application pools.
Use separate application pools if each application needs different access to system resources. (Can use multiple process accounts)
If an application is a resource hog, mission critical, or an "unknown", it is best to put it in to its own pool to isolate it from the rest of the system
We work as outside contractors for a large corporate client. We are not on-site, so we do not have connectivity to all of their systems. Sometimes during development it is necessary for me to debug an application directly on their development servers. To do that I must be able to attach to w3wp process. When I attach and start debugging, entire process stalls, which affects all of the applications that are in the same process/application pool.
By creating a dedicated application pool and moving my development there, I can easily debug without making anyone's life miserable.
What are pros and cons of having dedicated application pools over keeping web applications in one default app pool?
Pros:
Applications are isolated from each other, unless IIS goes with it, an app pool locking will only take out applications in that pool
Ability to run applications under different ASP.NET runtimes, one pool for 1.1 another for 2.0 if needed
Ability to have different app pool settings for more or less critical applications. For example a corporate website in ASP.NET might want to have the shut down after __ minutes of inactivity bumped up, to prevent unloading because response is critical. Other sites might not need it.
Can secure pools from each other in regards to file access, great for third party, or untrusted applications as they can run under a very restrictive user account.
Cons:
Each application pool has its own bank of memory and its own process, therefore CAN use more resources
Some find it hard to debug the application as you have multiple processes
The primary reason for combining sites in app pools is to conserve memory. There's a large memory overhead in running several w3wp.exe processes. If you have no specific reason for splitting them up, it's better to keep them together.
Dedicated app pools typically will keep problems occurring in one site from effecting the others. If you share app pools across sites, you could bring down all sites on the box when an error condition exists for only a specific site (or app pool).
Also, if you are mixing versions of ASP.Net on the same web server, you will need different app pools per ASP.Net version at a minimum, or do it per website.
I can't think of a good reason not to separate app pools, it is so easy to do.
I agree with Jason.
Also, you can designate different users (such as a Windows account) for different app pools. That enables setting up those users with different permissions in the database. That helps enhance security, and enables tracking which website/user is hitting the database, useful when tracing database performance issues.
If you have separate apppools then you pay a penalty in the initial load time of the first person to visit your site and spin back up the apppool after it recycles.
For example let's say overnight no-one hits your server, IIS will spin down (default 20mins I believe). The first person to visit the server will suffer a delay until the your application has been loaded back into memory.
Depending on how you deploy your site (e.g. release mode etc..) this will either not be a problem or could be annoying.
This is why we are looking into moving to a single apppool/server rather than 1 for each site.