Questions follow dots. The rest is history and system hardware/software.

It is an internal 3TB Hitachi drive that has 5 reallocated bad sectors on my:

  • MacPro 5,1
  • 3.33 GHz 6-Core Intel Xeon
  • 24 GB memory
  • OS 10.6.8
  • Boot 200 GB SSD

Have prepared new drive - zeroed out, 1 partition, Mac OS Extended (Journaled), GUID, (also 3 TB 7200rpm Seagate Barracuda)

Currently: Me Read & Write, Admin Read & Write, and Everyone Read Only

  • Want to add System - Read & Write. Is this necessary? Is best way via terminal or simple alternate way for non-geeks?

I don't rely on Time Machine, do frequent data backups, and clones of Boot Drive, and backups of User Folder; however still use Time Machine, just in case.

History: When SmartMon Tools told me 5 bad sectors, I panicked and thought maybe I should delete some of the older backups, as I saw drive was filling up; mistake #1.

When I realized it was a mistake, I tried to put back one of backups in Time Machine; but aborted that and managed to delete 3 backups from trash holding down option key.

Given this erratic behavior on my part and the failing (5 bad sector) Time Machine HDD: Is it best to start with fresh prepared HDD and just do a new clean Time Machine backup? (rather than cloning questionable old Time Machine HDD with CCC)

From research: Doesn't seem to be easy way to verify data (current backups) as it seems in 10.6.8 asking Time Machine to Verify Backups (with option key) only verifies that the Disk image is not damaged.

My new Time Machine HDD is currently in external bay. Plan to replace "failing" HDD with new one - internal on Mac Pro, once I decide how to proceed.


If the question is whether you should trust the current TimeMachine backup or not, I don’t believe 5 bad sectors is anything to panic about… Yet… It means the drive is slowly dying but is in decent shape now. Whether those 5 bad sectors have data or not is unclear, but I would recommend you do the following.

You say this:

My new Time Machine HDD is currently in external bay. Plan to replace "failing" HDD with new one - internal on Mac Pro, once I decide how to proceed.

If one drive is connected in an external bay, and the other is set internally, I would download a tool like Carbon Copy Cloner and do a clone of the current TimeMachine drive to the new drive. And then when that is done, swap out the old drive for the newly cloned copy.

If somehow that fails due to the bad sector issue, then you can just swap out the failing drive for the new drive and start anew. But by attempting to make a clone of the drive with Carbon Copy Cloner you will at least have a fighting chance to restore your already established TimeMachine setup.

  • Thanks, Jake: Do you think that Carbon Copy Cloner will "refuse" to clone if there are issues with current data on old Time Machine drive? You can verify data if you sync with Chronosync; but is it better to clone Time Machine drive? (in which case I would use CCC) – Barbara Nov 19 '14 at 9:42

We use a product named Scannerz (http://scsc-online.com/Scannerz.html) to do testing. The nice thing about it is it can do other system tests like cable checks, sector checks, system checks, etc. and it can detect degradation SMART testing misses. It checks SMART status but doesn't alarm you when trivial events occur, whereas most SMART testing software tends to over-alarm people, especially SSD users, when a sector remap occurs.

A 5 sector remap on a drive with 3TB of data is peanuts. A typical HD crash will often yield gigabytes of bad data on an HDD. The trouble with SMART testing is that it only detects problems after an attempted write operation fails. This is why we use Scannerz. It scans the entire drive, even if an attempt to write to it has never been made. If you have a true and serious head crash or the drive is truly failing, you'll know. It scans the media only and pays no attention to whether or not the system ever tried to write to the drive. It is not a repair tool. True repair tools don't exist for hard drives. The disk controller controls everything. The only real way to properly re-map bad sectors is to zero the drive (as you've done) and if it fails, forget it, because it means all the spare sectors are used up.

If you zeroed the drive and Disk Utility succeeded, then the problems probably aren't that severe. If you attempt to clone the drive using CCC and there are bad data blocks that actually contain data, CCC should flag them. CCC is only going to copy over blocks that are in use, not blocks that have never been used or that contain deleted files.

If the damage is truly limited to 5 sectors, especially on a drive that size, I don't know if it's really anything to worry about.

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