On Thu, 19 Feb 2015, John Andre Taule wrote:
Hi!
Case: mdadm Raid 5 4 2TB disks. ext4 formatted spanning the raid.
Attack: dd if=/dev/zero of=/dev/sdb bs=1M
Expected result would be a raid that could be recovered without data loss.
Result was that the file system failed and not possible to recover.
As I understand it if this was a "hardware type fake" raid controller, the
outcome would be uncertain. However I'm a bit confused as to why the raid
(or more specifically the file system) would fail so horrible when losing
one disk. Is there perhaps critical information written "outside" the raid
on the physical disk, and this where overwritten in the attack?
Did you stop the array before you did the dd command, or you just did it?
If you just did it, most likely you overwrote the superblock on the drive
(located near the beginning of the drive by recent default), plus part of
the file system.
It would be nice to have an exact idea as to why it failed so hard, and
how obvious it should be that this attack would have more consequence
then a degraded raid.
Because if the drive was active then the operating system most likely
didn't notice that you overwrote part of the data on the disk and the
drive wasn't failed.
--
Mikael Abrahamsson email: swmike@xxxxxxxxx
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