Drobo

Time Machine won't backup

I installed Drobo with four mixed-brand hard drives to use as my Time Machine backup. It went well for a week, but now Time Machine will not backup to Drobo. I get a Mac window that says Time Machine was not backed up because an error occurred copying the files.Before installing Drobo I used Time Machine successfully for years without problems, so I suspect Drobo is the problem. The last failed backup attempt I got this message from Time Machine Buddy:

Starting standard backup
Backing up to: /Volumes/Drobo Large Partition/Backups.backupdb
No pre-backup thinning needed: 1.50 GB requested (including padding), 13.02 TB available
Copied 1 files (0 bytes) from volume Scratch Disk 2.
Waiting for index to be ready (100)
Error: (-36) SrcErr:NO Copying /Users/TonySiciliano/Pictures/Eastern Sierra Oct 2010/Eastern Sierra Oct 2010 Keepers/36, 628, 630 Eastern Sierra Oct 2010 as Smart Object-1.psd to /Volumes/Drobo Large Partition/Backups.backupdb/Anthony Siciliano’s Mac Pro/2010-10-12-162007.inProgress/04705EC3-610F-449C-A7EC-D0D6D870552B/2.0 TB Boot Hard Drive/Users/TonySiciliano/Pictures/Eastern Sierra Oct 2010/Eastern Sierra Oct 2010 Keepers
Stopping backup.
Error: (-8062) SrcErr:NO Copying /Users/TonySiciliano/Pictures/Eastern Sierra Oct 2010/Eastern Sierra Oct 2010 Keepers/36, 628, 630 Eastern Sierra Oct 2010 as Smart Object-1.psd to /Volumes/Drobo Large Partition/Backups.backupdb/Anthony Siciliano’s Mac Pro/2010-10-12-162007.inProgress/04705EC3-610F-449C-A7EC-D0D6D870552B/2.0 TB Boot Hard Drive/Users/TonySiciliano/Pictures/Eastern Sierra Oct 2010/Eastern Sierra Oct 2010 Keepers
Copied 2871 files (605.0 MB) from volume 2.0 TB Boot Hard Drive.
Copy stage failed with error:11
Backup failed with error: 11

Any help would be appreciated!!
Mac Pro 2x2.66, OS 10.6.4

First, you should try to rebuild the Drobo directory using DiskWarrior.
If you don’t have DiskWarrior, you may try to repair using Apple’s own Disk Utility, although success is not guaranteed.
That may, or may not, cure your Time Machine problem.

It may be totally unrelated to your own problem, but in the past, I also had major problems with Time Machine on a regular FW400-attached disk : once every 2 weeks or so, the Time Machine directory was destroyed, Time Machine would refuse to run anymore and I had to do a (lengthy) rebuild of the Time Machine directory using DiskWarrior.

I finally discovered that problem occurred when the Mac was going to sleep while Time Machine was updating the saved files : for whatever reason, this destroyed the directory.
The solution was to build a script unmounting the Time Capsule before going to sleep, and remounting it when awakening.

As a final note, I am afraid using a Drobo single partition for Time Machine will likely slow it down a lot for all other files accesses, because of Drobo increased fragmentation due to x0 000 files.
Using a separate partition, as explained in this DRI support note should improve performance for non Time Machine accesses.
Note also that Time Machine partition should be the first one, not expendable as you add Drobo disks.