[Lustre-discuss] Restoration of mds is of a different size!
Dilger, Andreas
andreas.dilger at intel.com
Thu Dec 20 10:15:25 PST 2012
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
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