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TOPIC: surface scan taking a very long time

surface scan taking a very long time 28 Jun 2017 08:31 #8417

sorry if this is a duplicate post, I posted this earlier, but for some reason my post didn't show up, so I'll type this again...


I have 3 identical drives in a Mac Pro, they all pass all tests (smart check, surface scan...) but 1 of the 3 drives takes more than 10 hours to scan, the other 2 take 3,5 hours to complete.
Read and write speeds for this drive are also unusably slow (which I why I bought Techtool to check what was wrong).

Since no clear error shows up in Techtool, what could be causing this problem ? Could this be a mechanical failure of the drive ? Wouldn't that show up in the smart report ?
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surface scan taking a very long time 28 Jun 2017 10:05 #8418

The forums are moderated. New postings do not appear until they are approved by a moderator.

The Surface Scan test reads blocks on the drive, one after another. The total time depends on drive speed, CPU speed, the speed of the bus to which the drive is connected, and possible interruptions from other processes. It is intended to detect unrempapped bad blocks, but is not intended to be a benchmarking program for drive performance.

S.M.A.R.T. testing deals with some characteristics of a drive that could affect read and write performance, such as the Seek Error Rate (attribute seven) and the Seek Time Performance (attribute eight), but I do not recall anyone using S.M.A.R.T. tests who found a failure of these attributes associated with noticeable drop off in read and write performance.

I suggest that you look at the All Messages log or its equivalent in the more recent system software and see if there are a lot of i/o (input/output) errors being reported. Also, contact the maker of the drive mechanism and see if they can suggest a benchmarking program so you can compare the performance of the three identical drives. It might be worth the trouble to swap the position of the drive that is currently slower to a different position, and see if that affects its performance.
MicroMat Inc
Makers of TechTool
Last Edit: 28 Jun 2017 10:07 by micromattech3.
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surface scan taking a very long time 28 Jun 2017 10:45 #8419

Many thanks for explaining that.

I wasn't trying to use Techtool as a benchmarking app... I know for sure something is wrong with this disk and I should replace it asap... I was only hoping that Techtool gave me clear indication as to what is actually wrong with this disk.
This would help me diagnose and recognize future problems.

As it is now, I think I've gone through all the tests, but no error whatsoever has been reported at all. As far as Techtool is concerned, this disk is fine... which is clearly not correct.

I've dived into console and searched through the messages, but no input output errors pop up.
Isn't this something that could be built into Techtool as well ? i.e. when doing a defrag, this is reading and writing, isn't it ? Wouldn't that bring up input output errors ?

I'll try swapping the drive as you suggested, maybe the drive IS perfectly fine and one of my drive bays is faulty...
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surface scan taking a very long time 28 Jun 2017 11:00 #8420

You are welcome.

You can configure the TechTool Protection system preferences pane to check for i/o errors. They get reported periodically. I have an external FireWire drive that frequently shows i/o errors, not because of any defect, but because it has spun down and is not available to some process that was going to use it.
MicroMat Inc
Makers of TechTool
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surface scan taking a very long time 28 Jun 2017 11:11 #8421

I'll have to install the protection system then.. I had not done that as I do not want to have things running in the background.
I use this Mac Pro to edit huge video files and it needs all the juice it can get.
Does the protection system take up much resources ?
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surface scan taking a very long time 28 Jun 2017 11:28 #8422

No, and you can turn most ofthe processes used by the TechTool Protection system preferences pane of. You can also remove the pane using the Remove TechTool Protection menu choice in the TechTool Pro 9 menu of the application. I suggest that you make a screen capture of how you have the email alerts set up, once they are working properly, for future reference.
MicroMat Inc
Makers of TechTool
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