Re: [linux-lvm] Disk crash , LVM and ext2... (bis)

[Emmanuel Varagnat <emmanuel.varagnat@free.fr>]

Emmanuel Varagnat wrote:
> I played a bit with that, and it looks like when device-mapper can't 
> access a zone it returns zeros.
> What I did, is to create an LV over 4 or 5 partitions, format it, zeroed 
> the first partition, do a 'vgscan -P' and try to read the block device 
> (LV raw data).
> I supposed that this is the device-mapper that hide the missing 
> informations by returning zeros. Is there a way to know (via ioctl for 
> example) that a data is not available ?
> For my program, I need to know, what is readable and what is not readable.
> 

Do you think the LV_BMAP ioctl command could tell me if a block is 
available or not into the LV ?
Its purpose is to give the sector number and the drive of a logical 
block, isn't it ?

What I want from the LVM is to tell me if data returned by a read 
command can be trusted. If it returns me a lot of zeros is it because 
the block is not available or because the block effectivly contains zeros.

Thanks a lot.

-=( manu )=-