Re: Strange hardware problem, any clue is welcome
----- Original Message -----
> From: "B. M." <b-misc@gmx.ch>
>
> I have a really strange problem with an computer from this fruit company
> in my family:
>
> It's an iMac from 2008, still running osx 10.6, but I put Testing on it
> several months ago as the second OS (which is much better, as I
> think...). Therefore I shrinked the existing partition on the 500GB SATA
> hard drive and added a small boot partition and an ext4 partition for /.
> The system was fully encrypted.
>
> Unfortunately, there was a problem with disk I/O: booting into Linux
> went well, sometimes the machine worked normal, but most of the time it
> got very slow after some time (maybe after about an hour, sometimes
> earlier, sometimes never) during disk activity. It was very difficult to
> work with. After a warm reboot the firmware didn't find any disk most of
> the time but not always.
>
> Last week I replaced Testing by osx 10.10. The installation went well
> and it seemed that everything works. About an hour later I discovered
> the possiblity to enable disk encryption; what happens is that the OS
> sets a kind of partition flag and starts encrypting the partition on the
> fly, one can continue to work! - one can even shutdown the system and
> continue later. During this encryption process, the machine started
> hanging again and later it was completely stuck. After a forced reboot,
> it continued to encrypt but after a few minutes it's again stuck. This
> seems to be reproducable every time I reboot, so the machine is just
> unusable, the encryption is stuck at about two thirds. osx
> 10.6 didn't show these problems when it was used (without any
> encryption), even in the last couple of
> months, when Linux was already installed and showed the problems.
Lack of SMART errors aside, I would have thought it was bad sectors. Let's suppose OSX is installed on the first half of the hard drive, and all those sectors are good. Now you install Debian on the second half, and you hit bad sectors. Same thing happens when you remove Debian but encrypt OSX -- it most likely is encrypting the entire drive and not just the used space. So you hit the bad sectors again.
That would be my guess, but I don't know why you're not seeing any SMART errors.
-Rob
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