Why I should not perform a Restore-SPSite for a copy of a site collection on the same content database?

Question

I have read these links which talks about using Backup-SPsite && Restore-SPSite:-

• link1
• link2

and they both mentioned that restoring a copy of a site collection's back-up file file using Restore-SPSite will mainly create a new GUID for the site but will reserve the GUID for the site collection's components such as its subsite, content type, etc... so they mentioned that we should do the Restore-SPSite on a new Content Database to avoid GUID conflict..

so I did the following test:-

• I have the following site collection "http://..../businessfunctions".
• I backup it.
• then I restore a new site collection (http://..../testsite) using the backup file inside the same content database (Actually I only have one content database).
• and I did not get any exception,, or any error message about any GUID conflict..

so now I have 2 site collections (/businessfunction & /testsite), that have the same GUIDs for their; subsites, content types, etc... but I am able to work on these 2 site collections without having any problem.

So can anyone adivce why all the links which talk about Restore-SPSite mentioned that we need to restore on a different content database to avoid duplicate or conflict in GUIDs ??? In other words where I will face problems if I have for example 2 subsites that have the same GUIDs ,and their site collections are inside the same content database?? Here is a screenshot of the scripts which I perform:-

Answer 1

Just look at the code snippet below and try to imagine the scenario of what will happen:

using(SPSite site = new SPSite("http://somesite")) {
    using (SPWeb web = site.OpenWeb(SameGuid)) {
        return web.Url;
    }
}

The above code can raise an exception because two web objects would be returned, there are infinite scenarios where GUID is used to fetch an instance and every time there would be 2 cases:

1. It will take the first one (Worst case)
2. Throw an Exception (Developer will scratch his head!)

To maintain data integrity, avoid future hassle regarding scalability and enhancement, it is advised to restore Sp-Site under new Content DB.

GUID for a site collection is unique and it gets stored along with the site collection backup. Your content database has a table called dbo.sites with a column named "id"

At the end I would just say that even if you are able to Restore-SpSite with some workaround, it would be a big design flaw and would create problems in the future as this blog states.