2017-05-01 18:57 GMT+02:00 Pranith Kumar Karampuri <pkarampu@xxxxxxxxxx>: > Yes this is precisely what all the other SDS with metadata servers kind of > do. They kind of keep a map of on what all servers a particular file/blob is > stored in a metadata server. Not exactly. Other SDS has some servers dedicated to metadata and, personally, I don't like that approach. > GlusterFS doesn't do that. In GlusterFS what > bricks need to be replicated is always given and distribute layer on top of > these replication layer will do the job of distributing and fetching the > data. Because replication happens at a brick level and not at a file level > and distribute happens on top of replication and not at file level. There > isn't too much metadata that needs to be stored per file. Hence no need for > separate metadata servers. And this is great, that's why i'm talking about embedding a sort of database to be stored on all nodes. no metadata servers, only a mapping between files and servers. > If you know path of the file, you can always know where the file is stored > using pathinfo: > Method-2 in the following link: > https://gluster.readthedocs.io/en/latest/Troubleshooting/gfid-to-path/ > > You don't need any db. For the current gluster yes. I'm talking about a different thing. In a RAID, you have data stored somewhere on the array, with metadata defining how this data should be wrote or read. obviously, raid metadata must be stored in a fixed position, or you won't be able to read that. Something similiar could be added in gluster (i don't know if it would be hard): you store a file mapping in a fixed position in gluster, then all gluster clients will be able to know where a file is by looking at this "metadata" stored in the fixed position. Like ".gluster" directory. Gluster is using some "internal" directories for internal operations (".shards", ".gluster", ".trash") A ".metadata" with file mapping would be hard to add ? > Basically what you want, if I understood correctly is: > If we add a 3rd node with just one disk, the data should automatically > arrange itself splitting itself to 3 categories(Assuming replica-2) > 1) Files that are present in Node1, Node2 > 2) Files that are present in Node2, Node3 > 3) Files that are present in Node1, Node3 > > As you can see we arrived at a contradiction where all the nodes should have > at least 2 bricks but there is only 1 disk. Hence the contradiction. We > can't do what you are asking without brick splitting. i.e. we need to split > the disk into 2 bricks. I don't think so. Let's assume a replica 2. S1B1 + S2B1 1TB each, thus 1TB available (2TB/2) Adding a third 1TB disks should increase available space to 1.5TB (3TB/2) _______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://lists.gluster.org/mailman/listinfo/gluster-users
