Lustre 1.6 Operations Manual

15.1.2 Performing Device-level Backups
In some situations, you may need a full, device-level backup of an individual MDS
or OST storage device (before replacing hardware, performing maintenance, etc.). A
full device-level backup is the easiest backup method and it ensures preservation of
the original data.
In case of hardware replacement, if the spare storage device is available, then it is
possible to take a raw copy of the MDS or OST from one block device to the other, as
long as the new device is at least as large as the original device. To do this, run:
dd if=/dev/{original} of=/dev/{new} bs=1M
If there are problems while reading the data on the original device due to hardware
errors, then run the following command to read the data and skip sections with
errors.
dd if=/dev/{original} of=/dev/{new} bs=4k conv=sync,noerror
In spite of hardware errors, the ext3 file system is very robust and it may be possible
to recover the file system data after running e2fsck on the new device.
15.1.3 Performing File-level Backups
In some situations, you may want to back up data from a single file on the MDS or
an OST file system, rather than back up the entire device. This may be a preferred
backup strategy if the storage device is large but has relatively little data, parameter
configurations on the ext3 file system need to be changed, or to use less space for
backup.
You can mount the ext3 file system directly from the storage device and do a filelevel
backup. However you MUST STOP Lustre on that node.
To do this, back up the Extended Attributes (EAs) 1 stored in the file system. As the
current backup tools do not properly save this data, perform the following
procedure.
1. Lustre uses EAs to store striping information (location of file data on OSTs).
15-2 Lustre 1.6 Operations Manual • September 2008