On Fri, Sep 26, 2014 at 5:57 PM, Ric Wheeler <rwheeler@xxxxxxxxxx> wrote: > reflink for backup is really a bad idea since you will not have really made > a second copy - if the disk fails (even partially!) you might lose data > since we will not have a second copy of the blocks. Where it is not > supported, you will still need to do a full file copy which means normal > file operation speed for the backup and restore. Perhaps I didn't express the feature well enough, but here is what I think would be particularly useful, and how the reflink operation can make this extremely powerful. The below description works for the single server use case, but does not (AFAICT) yet exist for the multi machine Gluster scenario. When running an incremental backup with something like rsnapshot, only changed files are copied. Therefore in this common scenario you actually only have one copy of each current file, and each file that is the same across snapshots is in fact a hardlink to the same data. To do a restore, the operation could take hours, days, or even longer depending on how much data is present. If you cp --reflink, then you effectively complete the copy to restore location instantly (since the blocks don't need to be duplicated) and as they are COW files, changes happen as needed, without affecting the backup. Similarly, with a backup operation, many TB of data can be copied very quickly, because the data blocks don't need to move. The only problem with this scheme is that it only works for the single machine use case. Distributing it and replicating it across a scalable system like GlusterFS would extend this scheme to large data sets. I don't know how feasible that is, but I have been led to believe that it is. Hopefully the above use case is a compelling one. Any sysadmin who has sat and watched their data restore for 3 days knows the value of it. Cheers, James _______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://supercolony.gluster.org/mailman/listinfo/gluster-users
