Lustre discuss - Dec 2012 - Restoration of mds is of a different size!

Hello,

I am currently using lustre 1.8.  I am relatively new with lustre.  At the
moment, I am trying to move an mds/mgs system from one disk to another.

I used the version of tar modified by whamcloud in order to dump and restore the
filesytem.  I used mkfs.lustre to create a new mds/mgs filesystem on my
/dev/sdc.  I then I mounted the old mds at /mnt/mdsold and the new mds at
/mnt/mdsnew using filesystem type "ldiskfs"

I replicated the filesystem with the following command sequence:

cd /mnt/mdsold && tar ?sparse ?xattrs ?cf - . | (cd /mnt/mdsnew
&& tar ?sparse ?xattrs ?xvpf -)

However, look at the output of df:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sdd              2.3T  7.9G  2.1T   1% /mnt/mdsold
/dev/sdc              815G  3.1G  765G   1% /mnt/mdsnew


Now, why would the new filesystem use 3.1 gigabytes when the old one takes up
7.9G?

======================
Side note question: I have used the same version of tar to get a file-level
backup of my mds:

tar ?xattrs ?sparse ?cf - . >sdd.tar

The file created was 61 gigabytes in size.

Filesystem            Size  Used Avail Use% Mounted on
/dev/sdd              2.3T  7.9G  2.1T   1% /mnt/mdsold

Why is this?  Do the attributes take up extra space?

Thanks!
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
http://lists.lustre.org/pipermail/lustre-discuss/attachments/20121218/f83f4f7e/attachment.html

On 2012-12-18, at 16:39, "Jason Brooks" <brookjas at ohsu.edu>
wrote:
> I am currently using lustre 1.8.  I am relatively new with lustre.  At the
moment, I am trying to move an mds/mgs system from one disk to another.
> 
> I used the version of tar modified by whamcloud in order to dump and
restore the filesytem.  I used mkfs.lustre to create a new mds/mgs filesystem on
my /dev/sdc.  I then I mounted the old mds at /mnt/mdsold and the new mds at
/mnt/mdsnew using filesystem type "ldiskfs"
> 
> I replicated the filesystem with the following command sequence:
> 
> cd /mnt/mdsold && tar ?sparse ?xattrs ?cf - . | (cd /mnt/mdsnew
&& tar ?sparse ?xattrs ?xvpf -)
Looks correct. 
> 
> However, look at the output of df:
> 
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sdd              2.3T  7.9G  2.1T   1% /mnt/mdsold
> /dev/sdc              815G  3.1G  765G   1% /mnt/mdsnew
> 
> 
> Now, why would the new filesystem use 3.1 gigabytes when the old one takes
up 7.9G?
Perhaps different inode size, or fewer total inodes?
> ======================> 
> Side note question: I have used the same version of tar to get a file-level
backup of my mds:
> 
> tar ?xattrs ?sparse ?cf - . >sdd.tar
> 
> The file created was 61 gigabytes in size.
> 
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sdd              2.3T  7.9G  2.1T   1% /mnt/mdsold
> 
> Why is this?  Do the attributes take up extra space?
Tar is padding each file up to 20kB or something like that. 

Cheers, Andreas