Add'l ideas to cure slow Time Machine backup

Question

Over the past 10 days, the average duration of my Time Machine backups has gone from 1 minute to :42-:45 minutes. There's been no significant shift in my computing behavior during that time. To fix, I've tried nearly everything recommended in Pondini's terrific site -- can you see something that I've overlooked?
* iMac8,1 4GB, running OS X 10.6.8
* TM drive: Seagate GoFlex 1TB, 30 days old, was freshly formatted and 100% dedicated to TM; have tested both Firewire and USB; 356GB used
* Fusion virtual machines excluded from TM via Preferences
* no virus program running
Review of backupd items in system.log shows, after the first few weeks of speedy TM backups, a gradual decay -- can't pinpoint a cliff (that could be blamed on an installation, etc.) And there's no other TM-related messages ("deep traversal," etc) in the log. When I watch Activity Monitor during a TM cycle, I see low CPU usage by TM, and slow read/write speeds for disk activity.
Yes, I have:
* repaired permissions (frequently)
* done disk verify and repair on both internal and TM drives (nothing found)
* set drives to "no sleep"
* disabled Spotlight
* relaunched Finder (and, of course, rebooted the whole system)
* tested in Safe Mode (no improvement)
* run daily/weekly/monthly maintenance scripts and purged caches, using Cocktail (Ironically, it got dramatically worse yesterday after I did this!)
No, I have not yet reformatted the TM drive, nor reinstalled 10.6.8. Am I forgetting something else?
thx

Answer 1

Hi there
The same problem here:
17.07.12 17:17:17          com.apple.backupd[12749]          Starting standard backup
*means: com.apple.backupd[12749]
17.07.12 17:17:17          *          Starting standard backup
17.07.12 17:17:17          *          Backing up to: /Volumes/TIME MACHINE/Backups.backupdb
17.07.12 17:17:48          *          No pre-backup thinning needed: 703.6 MB requested
                                                  (including padding), 1.37 TB available
17.07.12 17:22:43          *          Copied 34006 files (639 bytes) from volume DATEN.
17.07.12 17:23:54          *          No pre-backup thinning needed: 704.0 MB requested
                                                  (including padding),1.37 TB available
17.07.12 17:27:14          *          Copied 10482 files (639 bytes) from volume DATEN.
17.07.12 17:29:47          *          Starting post-backup thinning
17.07.12 17:33:29          *          Deleted backup /Volumes/TIME MACHINE/Backups.backupdb/
                                                  pmg5/2012-07-03-121520: 1.37 TB now available
17.07.12 17:37:05          *          Deleted backup /Volumes/TIME MACHINE/Backups.backupdb/
                                                   pmg5/2012-07-03-114951: 1.37 TB now available
17.07.12 17:37:05          *          Post-back up thinning complete: 2 expired backups removed
17.07.12 17:37:06          *          Backup completed successfully.
Many years everything with TimeMachine was fine. No problems, no effort. Works quiet and effectiv in the background.
2 months ago I recognised first changes. TM needs long and longer. Thousands of files - big number with low volume - TM copied to my external HDD. "Preparation" and "reworking"  take a long time.
I controlled the backup with TimeTracker - a much smaller number of files was listed.
I read other threads:
https://discussions.apple.com/thread/3144862?start=15&tstart=0
and jump to Pandinis website. No success with this.
So long
iPille