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I believe it tombstones or whatever it's called in 30 days. &nbsp;So make haste if this is true or a lot of work will be needed.<br />
:)
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I think that the default setting is 60 days, but it can be changed.<br />
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You should be able to bring the repaired server online and have it replicate properly. &nbsp;On the other hand, if you have 3 DCs that are working properly I would consider removing and reinstalling AD on the server and then promote it. &nbsp;It should get everything it needs from the other DCs.
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thanks to all who contributed answers to my post. it is much appreciated. well done.
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note I assume this was just a hardware failure, and you didn't restore a backup of the DC.<br />
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&nbsp;If you did restore a backup of the DC, then DO NOT turn it on, that can cause major issues with your domain.<br />
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restoring DCs from backup requires a very specific set of steps, I find in that case its always easier to treat the DC as lost, clear the meta Data for it, build a new replacement DC from scratch and join it and then promote it verses dealing with getting the restore right.
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We had a backup server's hardware fail &amp;&nbsp;take out one of our secondary domain controllers with it. The failed dc is a writable Windows Server 2008 R2 but with no FSMO roles attached to it. The hardware has been fixed but the secondary dc has been offline for 26 days now. Is it safe to bring back online without any consequences?<br />
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Both our Primary (Windows Server 2012 R2) and two other secondary's (Windows Server 2012 R2 &amp;&nbsp;Windows Server 2008 R2) have remained online during this time frame and our functioning correctly.<br />
<br />
Thanks for your time.
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We had a backup server's hardware fail & take out one of our secondary domain controllers with it. The failed dc is a writable Windows Server 2008 R2 but with no FSMO roles attached to it. The hardware has been fixed but the secondary dc has been offline for 26 days now. Is it safe to bring back online without any consequences?

Both our Primary (Windows Server 2012 R2) and two other secondary's (Windows Server 2012 R2 & Windows Server 2008 R2) have remained online during this time frame and our functioning correctly.

Thanks for your time.

When is it too late to power back on a Secondary DC that's been offline for 26 days?

Windows Server 2008 and Windows Server 2008 R2, based on the Microsoft Vista codebase, is the last 32-bit server operating system released by Microsoft. It has a number of versions, including including Foundation, Standard, Enterprise, Datacenter, Web, HPC Server, Itanium and Storage; new features included server core installation and Hyper-V.

Windows Server 2008

Active Directory (AD) is a Microsoft brand for identity-related capabilities. In the on-premises world, Windows Server AD provides a set of identity capabilities and services, and is hugely popular (88% of Fortune 1000 and 95% of enterprises use AD). This topic includes all things Active Directory including DNS, Group Policy, DFS, troubleshooting, ADFS, and all other topics under the Microsoft AD and identity umbrella.

Active Directory

Windows Server 2012 is the server version of Windows 8 and the successor to Windows Server 2008 R2. Windows Server 2012 is the first version of Windows Server to have no support for Itanium-based computers since Windows NT 4.0. Windows Server 2012, now in its second release (Windows Server 2012 Release 2) includes Foundation, Essentials, Standard and Datacenter, and does not support IA-32 or IA-64 processors.