On Wed, May 03, 2017 at 05:11:04PM +0530, Shyam Prasad N wrote: > Hi, > > This email is actually several questions clubbed as one... > > I have a btrfs filesystem mounted at /btrfs_vol/ > Every N minutes, I run bedup for deduplication of data in /btrfs_vol > Inside /btrfs_vol, I have several subvolumes (consider this as home > directories of several users) > I have set individual qgroup limits for each of these subvolumes. > Additionally, I'm using btrfs-send/receive to backup each subvolume to > an identical btrfs filesystem on a remote server. > > I hope I've explained the setup clearly. Now, here are my questions: > 1. I understand that bedup does deduplication on whole-file basis. I > also read that duperemove works at extent level. > How do the two compare in terms of performance? > How stable is duperemove? I read a few posts suggesting bugs related > to extent-same. > duperemove seems ideal for my workload. However, have stayed away from > it, fearing instability. > > 2. Is it possible to have nested subvolumes (like in my tree > structure), and run btrfs-send and expect the data whole filesystem > (including all subvolumes) to be sent?
No, because send requires read-only snapshots, and the snapshot operation isn't recursive. So you can't send everything in one go. > My problem is that, since I send btrfs subvolumes, if there is any > dedplicated data between these subvolumes, it needs to send 2 copies > of the same data to the remote host. > You might ask why not have just a single subvolume and backup the whole thing. > But there are many cool features, like quotas and btrfs send/receive > based backup for selected user home directories, which works only at > the subvolume level. The solution to this problem is to use send -c repeatedly, sending the subvolumes one at a time, with one -c option for every subvolume that already exists on the receiving machine. So you'll do something like this: send snap1 send -c snap1 snap2 send -c snap1 -c snap2 snap3 send -c snap1 -c snap2 -c snap3 snap4 etc... Hugo. -- Hugo Mills | Gomez, darling, don't torture yourself. hugo@... carfax.org.uk | That's my job. http://carfax.org.uk/ | PGP: E2AB1DE4 | Morticia Addams
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