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TOPIC: volume optimization problems

volume optimization problems 10 Mar 2013 00:01 #3833

Attachment Screencapture1.png not found


I just upgraded to Mac 10.6.8. I run the volume rebuild utility first, and when I run volume optimization, it comes up with the error message;
volume’s directory is fragmented. I did the steps suggested, see attached, and that killed the system.

How do I fix the directory?

Rick
Last Edit: 10 Mar 2013 00:04 by micromattech3.
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Re: volume optimization problems 10 Mar 2013 00:13 #3834

I am sorry to see that you had this outcome after running volume optimization.

I do not see any attachment other than the screen capture. I cannot read the text in the window of the screen capture, even when it is enlarged by Preview.

The disk directory is repaired by the Volume Rebuild tool.

If by "killed the system" you mean that the disk directory is irreparably damaged, you should erase the volume with Disk Utility and restore the files from a backup. The program warns you to make a backup before you begin.

If the disk directory is not irreparably damaged, and the problem is that the disk directory itself is fragmented, you might be able to solve that problem by creating more free, contiguous space on the volume and then rebuilding the disk directory. The size of the largest unused block of disk space is shown in the Volume Optimization preview. The simplest way to create disk space that is both free and contiguous is by removing a large file, such as a movie, that is not now fragmented, after copying it to another volume.
MicroMat Inc
Makers of TechTool
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Re: volume optimization problems 11 Mar 2013 19:32 #3837

The text in the dialog box gives the same advice that is given in the manual section on using the cloning tool to work around the optimization problem posed by a fragmented disk directory.

Volume Cloning

The text in the dialog box states:

Volume's Directory is fragmented. It is not safe to optimize.

Restart from an eDrive:

From the original volume to a new empty volume do Volume Cloning File Sync Cloning.

From the new volume back to the original volume do Volume Cloning Duplicate Cloning.

When a volume is first formatted, it gets two files that record the locations of pieces of files, the Catalog B-Tree and the Extents B-Tree. (These two files are referred to as "volume structures", and pieces of files are called "extents".) The Catalog B-tree records the locations of the first eight pieces of a file. The Extents B-Tree, called the Extents Overflow file within Apple, records the locations of pieces of a file beyond the first eight.

The Catalog B-Tree is given a specific size that depends on the size of the volume. Apple makes an assumption about how many files are likely to be stored on a volume, and if the user puts more than that number of files on the volume, the Catalog B-Tree itself must grow, acquiring a new extent. If the sectors on the volume right after the Catalog B-Tree are occupied by pieces of another file, and the Catalog B-Tree must grow, then the Catalog B-Tree itself becomes fragmented.

An assumption is also made about the required size for the Extents B-Tree. If it becomes full, because the volume contains many files that have more than eight extents, and if the sectors after the Extents B-Tree are occupied, then the Extents B-Tree itself will become fragmented as it becomes larger and gains a new extent.

If you follow the plan described in the manual for copying the contents of the volume to another volume and then back again, and the Catalog B-Tree was the file that was fragmented, then the new Catalog B-Tree on both copies of the volume will also be fragmented, because the volume holds more files than Apple anticipated it holding. If the Extents B-Tree was fragmented because there were many fragmented files, it should not be on either copy, because the files are no longer fragmented.

When following the plan to clone the contents to another volume and back again, it is prudent to check the disk directory of each copy with the Volume Structures test or Disk Utility, and to make sure that the clone is bootable if the original volume was.

We hope that a future version of TechTool Pro will be able to optimize the disk directory.

Most files can grow by an amount as small as one block. The Catalog B-Tree and Extents B-Tree, in order to keep them from becoming very fragmented, which would degrade the performance of the filesystem, must grow by an amount of disk space called the "clumpsize". On my volumes, the now-obsolete utility hfsdebug showed the clumpsize to be 5 MB.
MicroMat Inc
Makers of TechTool
Last Edit: 12 Mar 2013 00:26 by micromattech3.
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Re: volume optimization problems 12 Mar 2013 02:00 #3838

I ended up building a new system, from scratch. I rebuild and optimized the new system, at every step. This gave me a working and optimized system. However, I wasn’t able to successfully clone the good system to another drive, with out having the same problem, using TechTools or CCC.

I am unclear on wether it is possible for TechTools to clone the system. Yes and how, or not at this time?

Rick
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Re: volume optimization problems 12 Mar 2013 02:20 #3839

Thanks for the update. It is good to see that you have a working system.

If you review the TechTool Pro manual pages linked above, and explore the Volume Cloning interface, you see that TechTool Pro can clone a volume either by copying files from one volume to another (Volume Cloning File Sync Cloning) or by copying blocks from one volume to a destination device (Volume Cloning Duplicate Cloning), which requires a device at least as large as the source volume, and which erases the destination volume.

If you had tried Volume Cloning Duplicate Cloning, try using Volume Cloning File Sync Cloning, even though it is slower than Volume Cloning Duplicate Cloning, because it copies files, rather than blocks.

It is very odd that Carbon Copy Cloner is unable to copy the good system to another volume. I suggest that you run the Surface Scan to check the intended destination device for unremapped bad blocks. Make sure that the destination device has the proper partition map (GUID partition map for Intel processors, Apple Partition Scheme for PowerPC processors; check using Disk Utility) and is formatted with at least one Mac OS Extended (journaled) volume). Make sure that you are not using Carbon Copy Cloner to copy blocks rather than files.

The Console application, located in /Applications/Utilities, may reveal helpful error messages that arose when you tried to clone the good system to another volume. Use Console to check the All Messages log entries at the time when you attempted to make the clone. There may be permissions problems here. Make sure that you are logged in as at least an administrative user when you attempt to make the new clone.
MicroMat Inc
Makers of TechTool
Last Edit: 12 Mar 2013 02:27 by micromattech3.
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