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REAR not backing up all LVM volumes #733
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@razorfish-sl could you paste the content of |
@razorfish-sl According the disklayout no Lvol from /dev/cinder-volumes was mounted at the time rear was running. Can you confirm this? If that is the case then this is how rear has been designed. Only deal with mounted FS, Lvols (of active Vgs). |
[root@core ~]# cd /dev/cinder-volumes but it is 'not' formally mounted to a mount point as in 'mount /dev/mapper/centos-spare /spare' it cannot be because the partitions are for use only by the internal virtualized systems, they are block devices only, their internal structure might not even be readable by the host os. You 'could' virtualize those block devices as 'files' in the host , but then you would have potential issues with fragmentation. |
@razorfish-sl So, to me, rear does what it needs to do - archiving the root disk; from your explanation it wouldn't make sense anyway to archive the cinder-volumes. |
how can the backup be worthless if I issued an init 1? |
@razorfish-sl Ok understood - just mount it for the sake of rear before running mkbackup then it will be taken into account. |
That may be problematic, since you would have to know & mount each block volume listed. |
@razorfish-sl is this feature request? Be able to include block volumes which are not mounted? Are how do you see it? |
Hi, With this "openstack" setup,some volumes are not 'physically' mounted to prevent the OS fighting over them. |
@razorfish-sl this is a very interesting use case you are bringing up here. Please keep in mind that ReaR was designed for a different purpose: Bare metal disaster recovery of a single server using an external backup solution. The internal NFS-based backup was added much later as a tool for quick testing and it is much less powerul as a backup solution than real backup software. By design ReaR operates on the filesystem level. That means that anything not mounted is out of scope for ReaR. The design goal of ReaR was to take a backup / layout snapshot of a running system so we never even considered thinking about doing an ReaR also has a very clear separation between structural information (e.g. LVM configurations) and file contents. The nice thing about structural information is that it does not change so fast while the system runs so that is perfectly OK to record it without any kind of quiescing. Filesystems and block blobs are the opposite: If you want to get a consistent backup then you must think about quiescing or you must have a system where it does not matter if the first 100 files/blocks are recorded 2 hourse before the last 100 files/blocks. With the system area of a server this is for most cases an acceptable risk. For a database filesystem this is certain death. @gdha was alluding to this issue when he wondered about the backup beeing worthless. We have already had other users who wanted to recovery Oracle data partitions etc. Or who wanted to include shared storage devices that where not mounted etc. That said, we will be most happy to get a pull request for new functionality and of course also help you develop it. Maybe backup concepts for cinder are yet to be developed. |
@schlomo I think this is not yet sufficiently explained in the rear I think it would help if 09-design-concepts.adoc |
I think #733 (comment) explains sufficiently why this particular issue currently contradicts the basic design of rear. Therefore I close this particular issue for now as "won't fix" which actually means "cannot fix" because it would require major design For the future I filed #769 "Brainstorming about fundamental enhancements for the backup". |
It seems that lvm volumes that contain block images do not restore correctly.
multiple LVM volumes over:
sda, 20gb
sdb , 350gb block image
Installed rear 1.17.2
setup NAS via NFS
dropped down to:
Init1
reconfigured missing network interface for ethernet
rear -v mkbackup
Total backup gz only 20gb
moved to secondary system, booted from iso
rear restore
sda restored
sdb MISSING....
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