I have a small domain with one server (domain controller - Server 2008 Std) and a handful of clients. In preparation for planning disaster preparedness, I have setup Windows Server Backup to backup the whole server daily. My concern is whether one domain controller is enough. For example, if this one server (domain controller) completely crashes, what happens next? In theory, I can rebuild this server by restoring my server backup. Is there any advantage to having a secondary domain controller in a crashed server scenario, other than no significant downtime while I rebuild the primary domain controller (via restoring from backup)? Any thoughts or advice would be greatly appreciated!

One is NEVER enough. Unless of course downtime is not a concern. In the case of a complete crash, do you have another server body of the same type, model, RAM, etc. to reload your backup on? Because if your crashed server is due to a catastrophic failure of hardware (MOBO, etc.) you won't be dropping your Server 2008 backups from say an IBM to a hastily purchased Dell or visa-versa. The System Restore backups are very picky as to where they are reloaded, and without the same type/model hardware, you will likely be scratch building a new domain. http://support.microsoft.com/kb/249694

One domain controller for a domain is not enough. You should at least have two domain controllers per domain. Let's suppose that you have an only one domain controller and it is down. Then at that time, you were restoring it. Until the end of restore, your users will be unable to logon (you can configure cached credentials to avoid that). Let's now suppose that you are unable to restore from a performed backup due to a certain error. What you will do at that time? You will lose your domain and all you AD objects and in this case you should create a new domain and imagine the administrative tasks that you will have. Now, let's suppose that you have got two domain controllers or more. If one is down, the others will continue to authenticate users and apply group policies ... Even if you are unable to recover the faulty DC, you will be able to force its demotion using dcpromo /forceremoval and then perform a metadata cleanup and resize FSMO roles that this DC was holder of them. Once done, you can promote it again and all will be back. So, as you see, one DC per domain is not enough and it is recommanded to have at least two domain controllers per domain. This posting is provided "AS IS" with no warranties or guarantees , and confers no rights. Microsoft Student Partner Microsoft Certified Professional Microsoft Certified Systems Administrator: Security Microsoft Certified Systems Engineer: Security Microsoft Certified Technology Specialist: Windows Server 2008 Active Directory, Configuration Microsoft Certified Technology Specialist: Windows Server 2008 Network Infrastructure, Configuration

DN: I do not have another server body of the same type. I'm sure this is very important to a certain extent. But to what extent? According to this article (http://technet.microsoft.com/en-us/library/cc755163.aspx), one of the most important concerns is ensuring the size of the disk on the new server is at least the size of the original disk. You're suggesting to plan to have a server with similar hardware on standby (or possibly as a secondary DC). Thanks! MX: This server is also where most of the data is stored (file server). If it fails, users cannot access data until a restore is completed. You're suggesting it needs to be determined how much downtime can occur before users need access to data. Can users log into Windows using XP/7 clients by default, when a DC (or all DC's) is down? Thanks! Have either of you had success with a full server recovery using Windows Server Backup? I will certainly be implementing a secondary DC soon. Thank you!

Have a look to this Microsoft article about cached credentials: http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/619.mspx?mfr=true In your case now, you should determine the average downtime and use your backups as a temproray solution. You should as soon as possible add an additional domain controller to your domain. Like that, you will ensure the high-availability of your domain. You can also ensure the high-availability of DNS service like that if both DCs are DNS servers holding primary AD-integrated zone of your domain and your client computers are using both servers as primary and secondary DNS servers. This posting is provided "AS IS" with no warranties or guarantees , and confers no rights. Microsoft Student Partner Microsoft Certified Professional Microsoft Certified Systems Administrator: Security Microsoft Certified Systems Engineer: Security Microsoft Certified Technology Specialist: Windows Server 2008 Active Directory, Configuration Microsoft Certified Technology Specialist: Windows Server 2008 Network Infrastructure, Configuration

ONE DOMAIN CONTROLLER IS NOT ENOUGH AS SAID BY OTHERS THE CONDITION TRUELY DEPENDS UPON THE CRITICALITY OF YOUR ENVIRONMENT AND NUMBER OF USER TIED UP WITH OTHER APPLICATIONS ON YOUR NETWORK!! Lets assume a scneario where you have only one server which is wind0ows 2008 goes down and . In the above scenario you would be reinstalling the operating system and restoring the System state data whihc means a downtime The time you will take to reinstall the operating system and restore the backups . Other Scenario with Additional Domain Controler The best thing would be having a an additional domain controller this additional domain controller will have all the replicated Active directory objects from the other windows 2008 server which mean a backup !! Incase if your main server goes down the users will never know that the main server is down as they will be working with the additional domain controller Note: you should have the Active directory integrated dns to acheive this. The only thing you would do this to give the full funtionality to you additional domain controller as your main domain cotroller wil be seizing the fsmo roles this way your users will not face any downtime. http://www.petri.co.il/seizing_fsmo_roles.htm Thanks http://www.virmansec.com/blogs/skhairuddin

Hello, i disagree with the others here, as one DC is enough in a domain to run it complete. In my starting times i did it for some years with a single DC domain, which also had Exchange installed(not recommended but supported from Microsoft). BUT for disaster recovery you must assure an AD aware backup solution and of course a single day full backup will not have all changes done throughout the day. So maybe multiple ones depending on your changes must be done. Recommended also by Microsoft are at least 2 DC/DNS /GC per domain as this provides failover and redundancy if one DC is down for short time(belo tombstone lifetime). Clients requrie a running DNS so make sure they are using both domain DNS servers on the NIC.Best regards Meinolf Weber Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.

Hello, i disagree with the others here, as one DC is enough in a domain to run it complete. In my starting times i did it for some years with a single DC domain, which also had Exchange installed(not recommended but supported from Microsoft). BUT for disaster recovery you must assure an AD aware backup solution and of course a single day full backup will not have all changes done throughout the day. So maybe multiple ones depending on your changes must be done. Recommended also by Microsoft are at least 2 DC/DNS /GC per domain as this provides failover and redundancy if one DC is down for short time(below tombstone lifetime). Clients require a running DNS so make sure they are using both domain DNS servers on the NIC. Best regards Meinolf Weber Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights

I support many customers with only one DC, until they can afford a second. If the one DC goes down, everyone is out of business until it is restored. As soon as they get another server class machine, I recommend they make it a DC for redundancy. Best is to have at least 2 DC's per domain (also DNS and GC's), and best if these DC's are dedicated just to AD. However, I feel it is better to have two DC's, even if one also runs another application, like SQL Server, than to have only one DC. Richard Mueller - MVP Directory Services

DN: I do not have another server body of the same type. I'm sure this is very important to a certain extent. But to what extent? According to this article (http://technet.microsoft.com/en-us/library/cc755163.aspx), one of the most important concerns is ensuring the size of the disk on the new server is at least the size of the original disk. You're suggesting to plan to have a server with similar hardware on standby (or possibly as a secondary DC). Thanks! As stated the need for the same hardware is rather clear according to Microsoft... They consider restoring from one hardware platform to another to be unsupported so you will not likely be able to get help from them.. I do not know your level of hardware/software expertise, but believe me... Moving from one machine to another one can be a nightmare. Expecially if you have third party RAID involved, dissimilar video, different network onboard (or cards), etc. Have either of you had success with a full server recovery using Windows Server Backup? I will certainly be implementing a secondary DC soon. Thank you! Haven't had to. We had three DCs. When one hiccuped it was easier (in the 2003 times) to pull it, rebuild it afresh, and join it back to the system. +++ I suggest that both DCs be same type/model for simplicity sake.... However, if money is tight, anything that can run Server 2008 well should suffice as a fall back position...