Volume Level source in File Level mode?

[lunadesign]

I have a D: drive with two top-level folders. I only want to back up one of them.

When I configure my backup, I specify the "File level backup (slower)" mode.

When I get to the part where I select the files, I've noticed that depending on how I interact with the UI, I can get the note next to "Local Disk (D:)" to say "> volume level backup" or "> file level backup (slower)".

I just ran a test where I tried each approach on a 3 GB folder tree with lots of folders and a mix of file sizes. To keep things fair, each test backup was performed after I deleted all the .vbk and .vib files.

Anyway, the performance difference was huge:
-- File Level: Data is read at 27 MB/s, entire backup takes 2 min 46 sec
-- Volume Level: Data is read at 282 MB/s, entire backup takes 0 min 48 sec

Is it safe to use Volume Level backups on partial volumes in this manner? Is there any downside?

[Mike Resseler]

Hi,

Volume level backup is indeed much faster compared to file level. In some cases you might be able to use volume level if your exclusions are limited. The problem with exclusions on volume level is that the system needs to build the exclusions from the snapshot and after a while that gives issues. There is not really a hard limit but it can hit it and your backups will fail at a certain point in time.

So my advice would be: Try out and see if it works, but keep the above in mind.

Mike

[lunadesign]

Hi Mike,

Thanks for the quick reply. Can you clarify what this failure will look like? IE, will it fail during a backup? Or will it silently work and then not work during a restore? Obviously the latter would be really bad.

And when you say "after a while", do you mean that it tends to fail down the road, i.e., after more incrementals have been added to the backup chain?

Thanks!

[Mike Resseler]

Hi,

The backup will fail. I believe you will get a notification of time-outs but I am not sure anymore, but it is certainly the backup that fails. I think you will get something like: Unable to exclude files from snapshot: Shadow Copy Optimization Writer timed out.

But if the backup succeeds, the restore will work also.

What I mean with after a while is a bad expression from my side, sorry. What I meant to say was that if you have more exclusions, and the list of exclusions grows, then it will fail. Volume level backup uses the VSS exclusion engine, and it can simply become too much for that engine to handle.

Hope it is more clear

Thanks

Mike

[lunadesign]

Hi Mike,

Thanks for the clarification. This is really helpful.