Small Business Server 2008 - Build document V. Backup, Restore and Disaster Recovery
SBS Native Backup and Restore (*)
There are many good articles about the SBS Backup and Restore Process on the SBS Official Blog and in other locations and we won't repeat all of that here. You can follow these links yourself and get a good understanding
of what SBS Backup does and how to use it.
Note that the above post was completely replaced on November 3, 2010, so if you haven't looked at it recently, you may want to go over there now and read it and the several follow on links. Highly Recommended!
If you ever had any doubts about the capabilities of SBS Backup, put them aside. You can absolutely depend on Windows Server/SBS 2008 Backup to create complete and useable backups of the entire SBS system,
including System State, SharePoint, Exchange and anything else you point to on your SBS Server. You can also exclude data items (but not system items) that you want to exclude, such as downloaded drivers, WSUS data files, and so on.
But, there are a number of things SBS 2008 Backup and Restore does not do and some details that are not fully explained in any readily available material that may help clarify the process and what you can expect.
First and foremost in considering your data and a potential disaster recovery, be aware that Windows 2008/SBS 2008 Backup uses Virtual Hard Disks to hold the backup data. Because Windows 2008 can only create
a VHD of 2048 GB, or for our purposes, 2 TB, source volumes that are 2 TB or greater will *not* be backed up by Windows 2008 native backup, and therefore will *not* be backed up by SBS 2008 Backup. This is a limitation of Windows, (or rather the NTFS file
system), not of SBS. Windows 2008 R2 offers a slight improvement in this regard, and SBS 2011, built on Windows 2008 R2 does also, in that it allows file and directory level backup, in addition to, or instead of, block level backups, thereby skirting the limit
imposed by block level backups that includes unused space on a block level backup.
Also, note that this restriction is lifted if the *individual* volumes are less that 2 TB. That is to say, you can have four 1.9 TB volumes in your SBS and SBS/Windows 2008 will perform the backup correctly,
assuming you can create a target that will hold 8 TB of backups, as you will need four individual 2 TB VHDs to hold it.
There is more to this story. SBS 2008 Backup requires breathing room. You can, but you should not, backup a 1 TB volume to a 1 TB Target. This will work as long as the source and the target are relatively
empty, but if you start to fill the source you will find that the target will fill also, and as it fills it will no longer accept the backup if significant changes have been made to the data. There is no hard rule here, but in general you want the target
to be 1.5 x the source volume(s), remembering the 2 TB limit for each VHD.
It is probably not necessary to point out, but since the question does come up, any additional servers or workstations in the SBS network are not backed up by SBS 2008 Backup. In particular this question arises
regarding the second Server 2008 and SQL offered in the SBS Premium package. You must configure backups for those systems separately.
It is possible to use more than one target drive for SBS 2008 Backup, in fact it is encouraged. The Official SBS Blog post referenced in the top of this article gives specific guidance on how to do this.
There is good reason to have at least three target drives instead of two. First, it increases the chances by 50% that you will have a working drive if you need it. Second, it means that if you have a policy to keep one drive out of the building at all times
you can accomplish this because there are only two in the building when you are changing target drives. If you ever find all three in the office at the same time, take one of them out to the car, preferably the one you just disconnected, assuming the SBS
Performance Report confirmed the backup was successful.
There have been instances of the order of the target drives, or the recognition of target drives by the SBS Backup becoming "out of kilter". While the cause is not clear, the symptom is a drive letter is added
to one or more of the target drives (which removes it from the SBS Backup pool). Deleting the backup logs, removing the drive letter and formating from the target, then clicking on Disable Backup, followed by running Configure Server Backup, should allow
one to "start fresh" with the two drives.
SBS 2008 will take quite some time to create the first backup on each target. This happens because the SBS Backup routine compares each and every block on the source to the target VHD and copies them from
the source to the target. Once that first copy has been made, subsequent backups to the same target will be much faster as only the changed bits are copied to the target. One thing to be aware of is that changing from Target1 to Target2 will result in longer
elapsed times for the next backup than if you had left Target1 in place, even if no changes have been made to the source. This apparently happens becuase SBS Backup verfies the integrity of the VHD and verifies what needs to be copied. If you change targets
and "backup now" you will notice the lag compared to leaving the original target in place and performing sequential backups.
In the usual case, SBS 2008 Backup is self maintaining. You should be able to run years of backups to the same target drives without any issues, because the backup process is intelligent enough to make room
for the current changed bits by clearing out the oldest ones. It does this with an "auto delete" feature that clears out the oldest bits.
There is one specific, and rare, case where a problem can arise: As the targets of SBS Backup become full you *may* find that your backups begin to fail with messages such as "0x80780030 media is full" error".
This error is caused by a very specific condition where the auto-delete feature deletes the older version of backups on the target disk by deleting the corresponding shadow copy. Each backup version is maintained in a volume shadow copy on the backup location.
Shadow copy of a volume is a read only copy of the volume and there can be multiple shadow copies on a volume which are maintained by tracking the changes on the volume and storing them in what is called "diff area files" on the volume. (The Diff Area is the
storage space that Shadow Copies of Shared Folders allocates on a volume for maintaining the snapshots of the contents of shared folders. A snapshot is a block-level set of information that represents the differences between the current content and content
from a previous point in time. The integrity of existing and new snapshots depends on the integrity of the Diff Area.)
The auto-delete feature, in order to ensure that at least some old backup copies are maintained on the disk, does not automatically delete backups if space utilization by older copies is less than 1/8 of the
disk size or in other words, 13% of the disk size. That means if the one full backup copy does not fit in the 7/8 of the disk size, backup may fail with the disk full error. Auto-delete will not automatically delete the last backup on the target. To recover
from this condition, you should:
Replace the target with a larger backup disk, remembering the 2 TB VHD per source volume limit, or the
vssadmin utility can be used to delete additional versions of backup from the target if they are not required. Here are the commands:
vssadmin list shadows /for=x: will list the shadow copies on x: and creation time.
vssadmin delete shadows /for=x: /oldest can be used to delete the oldest shadow copy on x: where x: is the backup location.
diskmgmt.msc can be used to assign drive letter to the backup disk temporarily and again removed.
Note that the vssadmin.exe tool requires an elevated command prompt.
Our summary here is that SBS Backup will do an excellent job of backing up your SBS, and, within the size limitations imposed by NTFS and the physical limits of squeezing too much data into too little space,
should be trouble free, excluding possible mechanical failure of the target drives, for the life of the server. One thing that is does not do, that some third party commercial programs purport to do, is to preserve the last copy of any deleted files. So if
you have been backing up to a target for some time, and you know or discover it is getting full, you may want to check that the first chapter of the bestselling novel you wrote two years ago is still alive and kicking somewhere.
Using ShadowProtect IT Edition for Disaster Recovery of SBS 2008.
(*content by Larry Struckmeyer)
To return to the outline of the SBS 2008 build document,