On 03/08/2014 05:48, NeilBrown wrote:
You are very unlikely to see UREs just be reading the drive over and over a
again. You easily do that for years and not get an error. Or maybe you got
one just then.
True. I read over 40 TB from this disk and I haven't find any error.
Some SMART attribute reported so far:
ID NAME FLAG V W T R
197 Current_Pending_Sector 0x0012 100 100 000 0
198 Offline_Uncorrectable 0x0010 100 100 000 0
As you can find, no error was reported, and I don't find anything
suspicious in dmesg. At least, this should prove that article as this
[1] are quite wrong.
Maybe URE errors are related to unsuccessful writes in the first place.
I will try to repeat the test intermixing read with full-disk writes.
[1]
http://subnetmask255x4.wordpress.com/2008/10/28/sata-unrecoverable-errors-and-how-that-impacts-raid/
If you want to see how the system responds when it hits a URE, you can use the
hdparm command and the "--make-bad-sector" option. There is also a
"--repair-sector" option which will (hopefully) repair the sector when you
are done.
NeilBrown
Thanks.
Il 2014-07-31 09:16 Gionatan Danti ha scritto:
Yes, you can usually get your data back with mdadm.
With latest code, a URE during recovery will cause a bad-block to be
recorded
on the recovered device, and recovery will continue. You end up with
a
working array that has a few unreadable blocks on it.
NeilBrown
This is very good news :)
I case of parity RAID I assume the entire stripe is marked as bad, but
with mirror (eg: RAID10) only a single block (often 512B) is marked
bad on the recovered device, right?
From what mdadm/kernel version the new behavior is implemented? Maybe
the software RAID on my CentOS 6.5 is stronger then expected ;)
Regards.
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Danti Gionatan
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