Re: [Fstransform-devel] preservation of hard links

[Massimiliano G. <mas...@gm...>]

On 11/03/14 01:45, Olaf Leidinger wrote:
> Heya!
>
> So this will reduce the amount of memory needed for the conversion?
>
> This would be marvellous! One backup directory set contains approximately
> 6 million hard links  (according to your find command). Thus, and to speed up
 > the conversion, I ordered the backup server to delete old backups and 
it's
 > still on it. At the moment, the file system is up to 50% free space 
(~5 TiB)
> again  (coming from completely full) . Yet, I doubt that the deleting+converting
 > is finished before my vacation, so I'll postpone it until after the 
vacation.
>
> Thanks for adding this new feature!
>
> Best,
> Olaf
>

Hello Olaf,

yes, the disk-based inode cache greatly reduces the memory needed by 
fsmove during conversion of file systems with a lot of hard links.
With it, the consumed memory does not depend at all on the number of 
hard links.

6 millions hard links could be managed also by the original code,
but "6 millions hard links in a single directory" makes me think that 
summing other similar directories, the original code may easily exceed 
the available RAM (it needed some hundred bytes per hard link).

With the new code, it shouldn't be a problem at all, provided you
specify with --inode-cache=DIR a file system with a LOT of free inodes 
(again, remember the command "df -i")

Regards,

Max