Re: [dm-devel] block mapping

[Zdenek Kabelac <zkabelac redhat com>]

Dne 29.9.2011 16:10, Kasatkin, Dmitry napsal(a):
> Hello,
> 
> 
> On Thu, Sep 29, 2011 at 4:42 PM, Zdenek Kabelac <zkabelac redhat com> wrote:
>> Dne 29.9.2011 15:35, Kasatkin, Dmitry napsal(a):
>>> Hello All,
>>>
>>> I would like to implement such block device, which can store
>>> additional information along with the block data.
>>> For example. so if file system has 4k block, I would like to store
>>> 4k+256b of additional information...
>>>
>>> Can such block device be implemented with device mapper?
>>>
>>
>> Yes - i.e.the old snapshot target stores the block and it's remapping info
>> (thought the size info is much smaller then 256b)
>>
> 
> 1. Old snapshot target? Where is it...
> 

kernel/drivers/md/dm-snap-persistent.c


> 2. Isn't it stores some data at the beginning of the block device - in
> the header..

A bit more complicated that this - but yes, quite straightforward target.


Zdenek