Re: Is Ceph recovery able to handle massive crash

[Wido den Hollander <wido@widodh.nl>]

On 01/08/2013 02:10 PM, Wido den Hollander wrote:
> On 01/08/2013 01:57 PM, Denis Fondras wrote:
>> Hello,
>>
>> I'm wondering if I can get every "rb.0.8e10.3e2219d7.*" from the OSD
>> drive and cat them together and get back a usable raw volume from which
>> I could get back my data ?
>>
>
> Yes, that is doable. The problem only is that RBD is sparse. So you'd
> have to fill up the empty spaces with 4MB of zeroes.
>
> But yes, it's doable if you gather all the objects and will the rest up
> with zeroes.
>
>> Everything seems to be there but I don't know the order of the rbd
>> objects. Are the last bytes of the file name the offset of the block ?
>>
>
> There was a quick perl command for this to generate all the suffixes,
> but I can't seem to find it right now.
>

You could do something like this to generate all the blocks you should 
need, the non-existing ones you should fill them with nothing, aka 4MB 
of nothing.

perl -e 'while ($s < (SIZE_IN_MB / 4)) { printf "BLOCK_PREFIX.%012x\n", 
$s; $s++}'

Size is the block-device in MB en BLOCK_PREFIX can be something like 
"rb.0.1016.238e1f29"

Wido

> Wido
>
>> Regards,
>> Denis
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