Deciding between System State Backup and Allcritical Backup in Windows Server 2008: Which one is the right solution for my needs?
(To learn more about System State Backups and how to run these in Windows Server 2008 please check http://technet.microsoft.com/en-us/library/cc742124.aspx)
Q) First of what exactly is an Allcritical Backup?
A) An Allcritical backup is a backup of all the critical volumes present in the system.
Q) What do you mean by critical volumes?
A) Critical Volumes refer to the volumes present on the system which house the Operating System and other files which are essential for the OS to function properly. In the event of a disaster these volumes are required to bring your server back up and running.
Q) If I take an Allcritical Backup, can I perform a System State Recovery and create a IFM dump of my AD server with it?
A) Yes you can! There is no difference between a SSR or a IFM dump done from Allcritical or System State Backup. Allcritical Backup is basically a superset of a System State Backup.
Q) Why Allcritical? If I have set up System State Backup of my server and my hard disk crashes, all I need to do now is reboot into my setup DVD and recover from the SSB, right?
A) Wrong. System State Backup will NOT give you disaster recovery from setup media . Windows Server Backup offers full disaster recovery from setup media, wherein if the entire machine goes down , user can simply boot into setup media and restore the entire machine to an older time. For using this feature you need to have an Allcritical backup.
Q) Fine, I don’t need disaster recovery and SSB’s are smaller than Allcritical Backups, so I guess I should go for SSB for my daily backup needs?
A) Actually no, Allcritical Backups backup the entire Volume while a SSB only backs up the relevant system state files so a SINGLE SSB will certainly be smaller than the Allcritical backup. But if you are considering to set up a daily backup , then one more thing to consider is that SSB’s are always full , All critical backups to volume and disks are stored in an incremental fashion. What this means is that if you take one backup that occupies ‘x’ amount of space on the backup target then second backup will only take up space required for the changed blocks ‘c’. Total space utilized on target for storing both the backups will be ‘x + c’. in case of an SSB if first backup takes up y amount of space then total space taken up for 2 backups will be (y)+ (y+c).
Q) How does this incremental storage work?
A) After creating the first backup , WSB creates a VSS snapshot on the backup target, so when the second backup is written on top of the first backup, only the changed blocks takes extra space as diff area. Thus making it space usage efficient. For more details on VSS, refer http://technet.microsoft.com/en-us/library/cc785914.aspx.
Q) I am seeing that Allcritical backups are pretty faster than SSB’s why is that?
A) This is because Allcritical backups back up volumes at Block level , so the backing up happens below the file system layer and hence are faster than SSB’s which need to first identify all files to be backed up and then back them up individually one by one. This again is not true always , if for example you have a 150 GB hard disk with 10 GB system data another 130 GB of other data like photos , videos etc then the Allcritical backup will certainly take longer time for completion than SSB since the amount of data is much more.
Q) Is there any other advantage that I can get by using Allcritical backups?
A) Yes, as a matter of fact there is. If you select faster backup performance in the performance settings menu, then the speed of the backup can be increased , so that only the changed information is transferred from the source to the backup target. But do remember that the IO performance on the volumes being backed up can be impacted. This is because Window Server Backup leaves a copy-on-write shadow copy behind on these volumes once the first backup is taken so that it can track changes made to the file system.
To Sum it all up:
|Type||System State Backup||Allcritical Backup|
|Incremental Target Usage||No||Yes|
|System State Recovery||Yes||Yes|
|Disaster Recovery from Setup DVD||No||Yes|
|Faster Backup Performance||No||Yes|
NOTE: This article applies only to Windows Server 2008. Windows Server Backup has many new exciting features in Windows Server 2008 R2 which we will be sharing in future blog posts.
Post by Suhas Rao