xfs_repair of critical volume

[Dave Chinner]

On Tue, Nov 16, 2010 at 11:29:41PM -0800, Eli Morris wrote:
> Hi Dave,
> 
> Thanks a lot for your help. I looked at the man page and elsewhere for this info and can't find what this means:
> 
> 
> extent: [startoffset..endoffset]: startblock..endblock
> 
> 
> I understand what an offset would be, but what the heck is a startoffset and an endoffset? 

startoffset: file offset of the start of the extent
endoffset: file offset of the end of the extent

> Is the formula for the location of the file:
> 
>  startoffset + startblock through endoffset + endblock, where the blocks and the offsets are in 512 bytes?

no.

> So this file:
> 
> 0: [0..1053271]: 5200578944..5201632215
> 
> would be contained from:
> 
> beginning: 	(0 + 5200578944) * 512 bytes
> ending:		(1053271 + 5201632215) * 512 bytes

No, it translates like this:

    Logical		  Physical
File Offset (bytes)	block on disk
-------------------     -------------
   0 (0..511)		5200578944
   1 (512..1023)	5200578945
   2 (1024..1536)	5200578946
 .....			.....
1053270			5201632214
1053271			5201632215

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com