Yesterday, a video demo of SBS 2008 backup was put up on Technet Edge. I've gotten a couple of questions that seem prudent to answer publicly instead of via email. I will do them in the standard Q&A format. If there are others, I'm happy to add to this post, simply e-mail me, and if it's something I can talk about regarding the backup, I will add it to this blog post.
Question: It sounds like it could re-introduce some of the hassles that differential and incremental backups used to pose for tape users. My understanding was that SBS tried to remove this complexity by enforcing daily full backups.
Sean: Great question. Each disk you plug into the system will have a full backup as the first backup to this disk. Each incremental backup, is the difference from the last incremental backup on that particular disk. E.g. If you plug in Disk-A, a full backup will be taken as the first backup, and every other backup will be incremental from that backup. If you unplug Disk-A on a Friday and plug in Disk-B, the same thing happens. When returning Disk-A to the system, the next incremental will be larger, as it does the incremental from when you unplugged Disk-A to get Disk-A back up to speed.
Question: External drives are generally IDE/SATA based and have a relatively high failure rate (often due to poor cooling). What happens when one fails? What if it’s the one that contains your very first backup?
Sean: We see a similar failure rate in most low-end tape drives, which are the ones that typically end up in our space. In addition to the disks being even more inexpensive, the lesser of two evils is the disk drive. This is why we recommend multiple disk drives for your backup, and we include backup status in the daily report so you can stay on top of such hardware failures. As mentioned in the previous question, both disks contain full backups, so there is no fear of loosing everything with one backup disk failing.
Question: When using external USB drives, the can have different drive-letters when re-plugging the drive. For example when someone has plugged a USB-drive or after adding DVD-drives, hard drives, will ‘SBS 2008 backup’ automatically find the USB-backup drive when it has another drive letter as before?
Sean: SBS Backup doesn't use drive letters, when you commit a drive to the backup application, the drive letter is removed and it doesn't show up in Explorer.exe. The SBS Backup application takes the entire disk for backups for multiple reasons. (1) Because you should keep back-ups on it, and not other data, and (2) the entire disk is converted to a specific structure to store the backups. The backup application accesses the disk via the low-level system APIs by a unique GUID, and thus knows the difference between the drives.
Question: When the end-user plugs the wrong backup disk into the server, will the server then do the correct incremental backup? For example: on Monday the server normally needs drive A, but the user attaches drive B.
Sean: Yes. Since it accesses the drive by unique GUID, it knows exactly which disk it's backing up to.
Let me know if there are any more questions, and I'll let you know if I can answer them.
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