Hi all,
I’ve been using WHS 2011 for a few years now, and even after all this time, I’ve still been somewhat confused about the 2TB limit and where it applies. So, I finally spent a day or so reading up on it and wanted to post a summary of what I understand. I believe everything I’m saying below is correct, but I've only tested some of it myself. If anyone has any experience to the contrary, please chime in!
Client Computer Backups:
- The total size of the client computer backup database is limited only by the size of the volume used to store it on the server. If you install a 4TB hard drive on the server and partition it into a single volume (using Disk Management in the server's Control Panel - since the WHS Dashboard limits you to 2TB), you can store 4TB of client computer backups on the server.
- WHS 2011 can back up MBR style client computers with volumes up to 2TB.
- With the UEFI/GPT hotfix (KB2781272) applied, WHS 2011 can back up GPT style client computers, including those with volumes larger than 2TB, as long as the server drive storing the backup database is large enough.
Shared files:
- There are no restrictions on the size of a volume used to store shared files. If you install a 4TB drive in the server, you can create a shared folder with 4TB of data.
Server Backups:
- Since the server backup utility stores backups as VHD’s, the maximum size volume it can back up is 2TB. However, each volume gets its own VHD file, so you can backup multiple 2TB server volumes onto a >2TB 512e compatible external disk (see below if you don’t know what 512e means!)
- Attempting to backup a 3TB volume containing less than 2TB of data will fail. However, using the Server Backup Snap-In by RDP’ing into the server desktop, you can configure backups of particular folders rather than entire volumes. In this way, you can back up folders from a server volume of more than 2TB as long as the contents of the folders do not exceed 2TB.
- Using the command line tool WBAdmin, you can create separate scheduled backups using the Task Scheduler to of particular folders, enabling you to create separate VHD’s for different <2TB folders on a single >2TB volume, effectively working around the 2TB VHD limit per volume.
- WHS 2011 stores multiple versions of server backups if you are backing up to a locally attached drive (i.e. not a network share). This version information is NOT stored within the VHD. So, the total size of all versions of the server backup of a particular volume may exceed 2TB so long as you are backing up the server to a large enough 512e compatible drive. (Versions are stored as Shadow Copies of the VHD files, not Shadow Copies within the VHD files, and are therefore not subject to the 2TB VHD limit.)
***What is a 512e disk?***: WHS 2011 server backup can only store backups on volumes with a 512 byte sector size. Most hard drives under 2TB have a 512 sector size. Most hard drives over 2TB have a 4096 byte sector size. Backup will fail with an “I/O error” message in the Event Viewer if you try to run a server backup onto a volume with 4096 byte sector size.
- HOWEVER: WHS 2011 can store server backups on a volume larger than 2TB if it supports 512e emulation (this is where the drive firmware emulates a 512 byte sector size despite the actual physical sector size being 4096 bytes). For external drives from Western Digital, reformatting them using WD’s Quick Format utility to the “Most Compatible” or “Factory Default” format option will enable 512e sector size and make them compatible with WHS 2011 server backup. I tested this myself with a 3TB WD My Book external drive.
In summary, if all of your server volumes are 2TB or less, you will have no problems backing up anything on your WHS 2011 server to a >2TB partition on a compatible 512e external disk using the Server Backup Snap-in tool. It only gets complicated when you have individual volumes containing more than 2TB of data, or if your computer backup database is >2TB. For volumes with more than 2TB of data, you can configure separate backups of particular folders using the WBAdmin command line tool. For a backup database larger than 2TB, you might consider a synchronization tool like SyncToy.
I hope this clears up some of the confusion, and I also hope I haven't stated anything incorrectly. Please reply and correct me if anything here is wrong! Thanks