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TOPIC: Volume Rebuild - FSRoot Tree rebuild...How long?

Volume Rebuild - FSRoot Tree rebuild...How long? 18 Jun 2018 18:04 #9841

How long do I wait before considering this task has hung?

1TB SSD, already passed Disk Utility tests.
I just thought, more fool me, that I could gain some confidence by running Volume Rebuild.
There is no progress report at all, just an incrementing timer, a spinning 'radar' icon & a green flashing light on FSRoot Tree.

Some indication of progress would be really useful.

Nearly 6 hours & nothing, nada, zilch...

I've lost the whole day waiting for it, I'm about to give up & leave it overnight. I daren't quit the task for fear of damage.
If it's still plodding in the morning I'll just give the damn thing up for dead & reformat/recover from Time Machine.

This is one task I will never trust again.

Put a progress indicator in it !!!
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Volume Rebuild - FSRoot Tree rebuild...How long? 18 Jun 2018 18:35 #9843

The interface for the Volume Rebuild tool in TechTool Pro 96.3 is fully described and illustrated in the manual for the program:

www.micromat.com/product_manuals/techtool_pro_96_manual.pdf

on pages 6.6 and 6.7 (pages 55 and 56 of 129 in the pdf file).

The manual is also available in the Help in the TechTool Pro application.

Progress is indicated by a series of green lights that light up in succession, with a particular stage of the rebuilding of the disk directory noted for each light.

Unless you have reached the stage where the Technical Comparison window (also show on these pages in the manual) has appeared, and you have clicked the Replace button, no change has been made to the disk directory. The process is read-only until the Replace button is clicked.

If another attempt fails, please send a message to This email address is being protected from spambots. You need JavaScript enabled to view it. . Thank you.
MicroMat Inc
Makers of TechTool
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Volume Rebuild - FSRoot Tree rebuild...How long? 18 Jun 2018 18:40 #9844

There is really no point in rebuilding the disk directory on an SSD unless it is known to contain errors. The errors themselves can be detected by the Volume Structures test, which is read-only.

I suggest you run the Surface Scan test to check the SSD for bad memory cells, in case that is the reason why the Volume Rebuild process made so little progress. If you are using High Sierra, running the Surface Scan requires booting from a bootable volume on a device different from the one to be scanned, due to changes Apple made in High Sierra.
MicroMat Inc
Makers of TechTool
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Volume Rebuild - FSRoot Tree rebuild...How long? 19 Jun 2018 09:33 #9851

OK, background to this issue...

I was having an issue with Time Machine claiming it couldn't back up...
"Time Machine could not create a local snapshot to back up from."
Checking the volume with Disk Utility showed there were 57 snapshots, which seems excessive. Further research led me to try thinning these...
refs:
apple.stackexchange.com/a/309144/85275 - which appeared to be successful &
apple.stackexchange.com/a/309950/85275 - which didn't.
TetsMac:~ glee$ sudo tmutil listlocalsnapshots /
Password:
com.apple.TimeMachine.2018-06-18-91750 am (dataless)
TetsMac:~ glee$ sudo tmutil deletelocalsnapshots 2018-06-18-91750
Error parsing argument 2018-06-18-91750
TetsMac:~ glee$ sudo tmutil deletelocalsnapshots 2018-06-18-91750 am
Usage: tmutil deletelocalsnapshots <snapshot_date>

the 'am' seems to be upsetting something, somewhere & i don't seem to be able to get rid of that last (dataless) entry.

Since then, I've been seeing issues issues with FSRoot Tree & Snapshot metadata.

I thought that running the Volume Rebuild might do the same thing as Disk Warrior used to on HFS+ drives; check, rebuild, fix.
I guess not.


I was running from the eDrive on macOS 10.13.4. My boot drive is 10.13.5.
I left it overnight & got back to discover TTP using 120GB RAM... mostly compressed as I only have 64GB & complaints that the disk was full [it previously had 400GB of 1TB free].
I cancelled the task & rebooted, as RAM wasn't being handed back.

Surface Scan, SMART & Partition Map ran clean, no issues.
Volume Structures, however, was erroring at FSRoot Tree

Several attempts at fixing via Disk Utility may have got the FSRoot Tree, but Snapshot metadata is still giving this...
Checking the snapshot metadata tree.
error: snap_metadata_val object (oid 0xfd4c0): invalid extentref_tree_oid (0x0)
Snapshot metadata tree is invalid.

This is where I am right now, trying to figure out what to do next.
1. Run a combo updater over the existing structure.
2. Clone the drive, reformat, clone back, or
3. Reformat from Recovery & hope Time Machine can restore sufficiently.

Trying the combo first seems 'safest' but may just be a waste of time. I'm guessing cloning will simply restore the bad snapshot metadata, whereas Time Machine would hopefully restore over a clean OS... but Time Machine is not current :/
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Volume Rebuild - FSRoot Tree rebuild...How long? 19 Jun 2018 09:54 #9852

Thanks for your clear and detailed report.

We do not recommend trying to rebuild the disk directory on a Time Machine volume. In order to rebuild a disk directory, the new disk directory files (the Catalog B-Tree and the Extents B Tree) must both be able to be held in RAM at the same time. If you have 57 snapshots of roughly the same data, then the Catalog B-Tree and the Extents B-Tree are roughly 57 times as large as the corresponding files for the source volume. Nobody has that much RAM.

I have used Time Machine since it was invented. In my experience, if I allow it to make automatic backups, it becomes corrupted in about six months. If I do the backups manually, it can go much longer. My oldest snapshot is from August 7, 2016.

If I had your problem, I would check to make sure that the current source volume is free of directory errors and contains what it should. I would make another backup of the source volume, using Carbon Copy Cloner, Super Duper, Chronosync, or another commercial disk utility that is intended to make bootable clones (your option #2). Then I would erase Time Machine and start over. You lose the older versions of the files, but at least you have the ability to update the Time Machine.

Time Machine should not be your only backup:

You might enjoy this harshly-titled, slightly dated, but still useful article:

11 Stupid Backup Strategies - TidBITS
MicroMat Inc
Makers of TechTool
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Volume Rebuild - FSRoot Tree rebuild...How long? 19 Jun 2018 10:22 #9853

Interesting article... funny in a slightly cringe-worthy way ;)

Fortunately, I don't quite fall into any of those 11 camps.
I do rely on Time Machine as my 'quick fix' backup [& have done for maybe 10 years, since I got my first Mac Pro 3,1] but I also have several clones - though these are never up to date, by their very nature.
I also have Backblaze, as my 'house-fire' insurance.
[& bits of stuff in iCloud but I don't really rely on that.]

My only real issue is I use POP3 email, with only a 1-day retention. I extend that to 1 month if I'm doing major updates etc, just in case, but I just dropped it back to 1 day only last week, as I'd decided High Sierra might just be livable-with now.

I'll go with your suggestion - clone; clean Time Machine & start over.

Will let you know how I get on... clone in progress...
Thanks for the help.

BTW, I wasn't rebuilding Time Machine, just my boot volume, with 57 snapshots :/
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Volume Rebuild - FSRoot Tree rebuild...How long? 19 Jun 2018 10:27 #9854

Thanks for the clarification. If the snapshots are of many files, then the disk directory is going too large to be rebuilt.
MicroMat Inc
Makers of TechTool
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Volume Rebuild - FSRoot Tree rebuild...How long? 02 Jul 2018 04:03 #9920

Mine reported volume errors and recommended a volume rebuild. That rebuild process has been on FSRoot Tree for 25 hours 40 minutes so far. 500GB Crucial MX500 SSD. It really would be nice to have some kind of additional visibility into the process. If it is "stuck in a loop" or something like that, is that written out to a log somewhere? Is there really no way to provide any type of "percent done" status? The FSRoot Tree light is still blinking so I GUESS everything is OK and I (and more importantly my wife) just need to be patient, but...
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Volume Rebuild - FSRoot Tree rebuild...How long? 02 Jul 2018 09:57 #9923

In some cases, a person can see in the system.log file that a program is "going around in circles", but much of the time, only a programmer can tell that. If you want to explore that possibility, please send message to This email address is being protected from spambots. You need JavaScript enabled to view it. . Thank you.

The feedback that is provided is done in steps, not percentages. Calculating percentages adds more overhead to the program, and makes the process take longer. If you have observed the estimated times that Apple provides with its installers and updaters, they are not very accurate.
MicroMat Inc
Makers of TechTool
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Volume Rebuild - FSRoot Tree rebuild...How long? 02 Jul 2018 20:09 #9926

Woke up this morning and the system was totally hung at 26 hours 29 minutes, all activity stopped, would not respond to mouse or keyboard input, had to hard shutdown the system. Giving up, will reformat as HFS+ and restore from Time Machine...
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Volume Rebuild - FSRoot Tree rebuild...How long? 02 Jul 2018 20:27 #9927

I am sorry to see that the process ultimately froze.

If you have not already reformatted the drive, I would appreciate it if you would save the system.log file so you can send it to This email address is being protected from spambots. You need JavaScript enabled to view it. . It may contain error messages that would help us to learn what went wrong. The system log can be read using the Console application, located in /Applications/Utilities. Thank you.
MicroMat Inc
Makers of TechTool
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Volume Rebuild - FSRoot Tree rebuild...How long? 02 Jul 2018 21:41 #9928

I was running TechTool Pro from a Protogo USB drive, but I'm not finding any system.log file on the Protogo file system when I mount it as a regular USB drive on another system...it wouldn't make sense to look on the damaged disk for it since I wasn't booted from that. So I'm not sure which system.log file might hold the logs. There is no "/Volumes/Mac OS X Minimal/private/var/log/system.log".
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Volume Rebuild - FSRoot Tree rebuild...How long? 02 Jul 2018 21:57 #9929

You are correct. The system.log file would be on the Protogo device. I am not sure why it was not there.

While writing my previous answer, I was distracted by a malfunction in my own system. The external drive with my Time Machine volume on it did not respond to anything. Launching Disk Utility never got past the stage where the disk information is gathered. After about 45 minutes of trying various things, I had to perform an improper shutdown. Fortunately, fsck_hfs automatically checked the Time Machine volume on the next boot.

It is possible that my external drive got too hot. This is a good time of year to remind people in the Northern Hemisphere that both computers and drives have maximum operating temperatures.
MicroMat Inc
Makers of TechTool
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