Re: BUG:write data to degrade raid5

[Kristleifur Daðason]

On Fri, Mar 19, 2010 at 6:20 PM, Joachim Otahal <Jou@xxxxxxx> wrote:
> jin zhencheng schrieb:
>>
>> hi;
>>
>> i use kernel is 2.6.26.2
>>
>> what i do as follow:
>>
>> 1, I create a raid5:
>> mdadm -C /dev/md5 -l 5 -n 4 /dev/sda /dev/sdb /dev/sdc  /dev/sdd
>> --metadata=1.0 --assume-clean
>>
>> 2, dd if=/dev/zero of=/dev/md5 bs=1M&
>>
>> write data to this raid5
>>
>> 3, mdadm --manage /dev/md5 -f /dev/sda
>>
>> 4 mdadm --manage  /dev/md5 -f /dev/sdb
>>
>> if i faild 2 disks ,then the OS kernel display OOP error and kernel down
>>
>> do somebody know why ?
>>
>> Is MD/RAID5 bug ?
>>
>
> RAID5 can only tolerate ONE drive to fail of ALL members. If you want to be
> able to fail two drives you will have to use RAID6 or RAID5 with one
> hot-spare (and give it time to rebuild before failing the second drive).
> PLEASE read the documentation on raid levels, like on wikipedia.
>

That is true,

but should we get a kernel oops and crash if two RAID5 drives are
failed? (THAT part looks like a bug!)

Jin, can you try a newer kernel, and a newer mdadm?

-- Kristleifur
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