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Re: Tool for detecting partition superblocks needed

Le jeudi 02 octobre 2008 à 20:17 +0200, Wolfgang Pfeiffer a écrit :
> Could this also be a simple file system damage?

Errors like that (i.e. in the middle of a DMA interrupt) are not simple
FS damage, I am pretty sure.

> I was hoping it was just something like that, because this hopefully
> could be "fixed" with a reinstall, and with a previous low-level
> formatting like
> dd if=/dev/urandom of=/dev/hda (not being sure whether the syntax is
> correct .. ) 

For this kind of low level formatting, I would advise you to dd
from /dev/zero, as the hard drive controller can try to replace bad
sectors if needed when it sees that an all-0 block is written. But when
some sectors begin to fail, others will soon come, in general.

> Oh, and the Fedora smartctrl found (surprise, surprise .. :) a failure on
> LBA 76724676 and 76724678, too (please see the old log above) ...

Well, this confirm that the error lies in hardware, not in the file
system itself.

> I attach the log made on the broken machine via 
> smartctrl -a /dev/hda

So, the very high numbers like Raw_Read_Error_Rate and Seek_Error_Rate
are meaningless, I think, but the numbers in Offline_Uncorrectable and
UDMA_CRC_Error_Count show that some sectors have already been lost. But
what worries me most is the Load_Cycle_Count value : 2898441 is far too
high for a disk, but may look real, as your disk as been spinning for
quite some time (10000+ hours). This roughly corresponds to a
load/unload every 15s : do you here some light "tic tac" sound from your
disk every 15s or so ? For reference, mine, which has a 8000+ hours
lifetime, has a count of 268656 (ten times less ...). If you take the
specs from seagate for your hard drive
( http://www.seagate.com/docs/pdf/datasheet/disc/ds_momentus5400.2_120gb.pdf ), you'll see it's made for at most 600000 load/unload cycles.

I am worried about it because this is what I saw from a lot of apple
laptops, and as you may have understood, from one of my lost iBook's
hard drive. This made the news some time ago, not especially for apple's
disks, but when Ubuntu was said to be killing hard drives : some vendor
BIOSes did not set the power saving mode of the hard drive "correctly",
which led them to load/unload too often, and kill the hard drive in a
very short time. AFAIK, OpenFirmware does not set any power saving mode
at all, and neither does OSX, and by default a lot of disk are in a
"maximum" power saving mode, which unloads the hard drive head very
often, thus consuming less energy but shortening the life of the hard
drive. For some years, I've been seeing a lot (4 from my eyes, more from
internet forums) of apple laptops fail after a bit more than a year
(mostly on "low end" laptops, like the iBook, whose hard drive is made
to bear no more than 300000 load/unload cycles). Most of them were not
using Linux, just OSX.

I don't know if this information should be louder spoken, because I
wasn't able to verify that on failing laptops I didn't handle but heard
to be failing quite soon in their life. But this is, I think, one of the
main reason hard drives seem so fragile today, as the autopsy shows that
the number of load/unload cycles really exceeded what the vendor says,
and as a lot of vendors want their laptop to save energy, they set
aggressive settings to gain some battery life.

You can change these settings with the -B option of hdparm, for
example :
  hdparm -B254 /dev/hda
disables power management on most hard drive (the value is drive
dependant, most of the time 255 or 254 disables power savings). I think
this is what is done in laptop-mode package when you set your hard drive
in "no PM" mode.
> > What do you mean by "see hda7" ? 
> to "see" in the sense of to "detect" ... 
> mac-fdisk detected the damaged partition in the Debian installer, IIRC
> ..

What I meant is that, if you can "see" some partition in mac-fdisk, you
can see them all. But this doesn't mean the FS on them is not failing.
When you said you didn't see hda7 but you did with the others, it
sounded strange to me.

> No, not that easily .. It's a Powerbook5,8: if I manage to remove the
> disk from it (there must be instructions somewhere on www) I'll
> reinstall a new one. No time to waste, because my old tibook, where
> I'm typing this email, is making strange noises already. Looks like
> I'm in need of quick decisions, besides working hardware   ... :)

Well, the instructions from macfixit are good, I already disassembled a
12" iBook and a 15" PB with them. And it looks like you will need them
soon ...

> > BTW, how old is your powerbook ? 
> a little more than 2.5 years. Still with the same disk installed that was
> shipped with the machine ..

My iBook lasted a bit more than a year, with an hard drive spec'ed for
half the load/unload cycle count ... make up your mind.


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