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TOPIC: Can one run a surface scan from a partition of the same physical drive?

Can one run a surface scan from a partition of the same physical drive? 04 May 2017 20:51 #8208

Small backstory: I'm defragmenting a Mountain Lion partition of around 400 GB from a Yosemite partition of around 100GB - both partitions are on the same drive, but the ML one has been running slowly and the ridiculous level of volume fragmentation has finally explained why (get this - 92 GB free space, largest contiguous block is 325MB... Thanks a lot, Apple "macs don't need to be defragmented" tech support :D :D :D

Anyway I'd like to surface scan this drive, because I began volume optimization more than 36 hours ago and it's only about 43% complete. Now before anyone says anything, I'm NOT going to abort this job because I can see that it is actually progressing, I'm very confident in TTP's abilities from past experience, and I'm a stubborn fecker who won't surrender to my robot overlord just yet ;) But the slow speed of this does make me wonder if there are dodgy blocks making the issue worse. Now I should point out that I *think* the issue here is the ratio of fragmented files to free space - 92GB free but also apparently 90GB worth of fragmentation in just 88 files (I'm guessing standard definition DVD rips, usually 4GB each, are the culprits here) - so maybe it's no surprise that it's going to take a few days to complete this job. But it has spooked me a little so I'd like to be absolutely sure there aren't any dangerous drive problems going on as well.

I don't currently have an external drive big enough to create an edrive from this mac (I have 8 GB memory, so the resulting eDrive would have to be at least 12GB and I think even more than this if I remember correctly) - is it possible to run a surface scan of this drive from a partition on the drive, or at least to just scan the partition I'm not currently booted from? I'm aware that a surface scan ignores partitions so really this comes down to whether a drive needs to be entirely unmounted in order to be scanned - anyone know if this can be done?

I'll get myself a new external HD in a week or so if I must, but I'm a little impatient so if I can run the surface scan as-is once this volume optimise is finished, I'd like to know. Cheers!
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Can one run a surface scan from a partition of the same physical drive? 04 May 2017 22:22 #8209

The forums are moderated. New postings do not appear until they are approved by a moderator. I deleted your earlier, shorter posting.

I am pleased with your confidence in our disk optimizer, but with so little free, contiguous disk space (shown as "Largest" in the Volume Optimization Preview window in TechTool Pro) it is going to take a very long time to optimize the volume. The amount of time depends on processor speed, drive speed, bus speed, and the exact distribution pattern of the file fragments and free space.

If you use the button to stop the disk optimizer, it should finish the task it is working on (the moving of pieces of one file), update the disk directory, and then stop. I suggest you do that, and then use this alternative method (which requires a second volume capable of holding all of the files of the one you are attempting to optimize):

Optimize Using the Cloning Tool

If the destination volume is larger rather than smaller than the source, you will have to use the File Sync Clone method each time you copy files. The Duplicate Cloning method makes a bit-for-bit copy of the source volume onto the destination volume, so the destination must be as large or larger than the source, because even the free space on the source is copied to the destination.

As a rule, you should have at least 15% free space on a bootable volume. (See posting 3537.)

The Surface Scan does not require unmounting any volume, and can be run from the active boot volume to examine its drive or any other available drive. It simply reads blocks, one after another, and makes no changes to anything other than the TechTool Pro log file.
MicroMat Inc
Makers of TechTool
Last Edit: 04 May 2017 22:27 by micromattech3.
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