On Mon, Apr 24, 2017 at 1:24 PM, Gandalf Corvotempesta < [email protected]> wrote:
> Il 24 apr 2017 9:40 AM, "Ashish Pandey" <[email protected]> ha scritto: > > > There is difference between server and bricks which we should understand. > When we say m+n = 6+2, then we are talking about the bricks. > Total number of bricks are m+n = 8. > > Now, these bricks could be anywhere on any server. The only thing is that > the server should be a part of cluster. > You can have all the 8 bricks on one server or on 8 different servers. > So, there is no *restriction* on number of servers when you add bricks. > However, the number of bricks which you want to add should be in multiple > of the > configuration you have. > > > This is clear but it doesn't change the result > As no one is using gluster to replicate data by loosing redundancy (it's > nonsense), adding bricks means adding servers > If our server are already full with no more available slots for adding > disks, the only solution is to add 8 servers more (at least 1 brick per > server) > > > > In you case it should be 8, 16, 24.... > > "can I add a single node moving from 6:2 to 7:2 and so on ?" > You can not make 6+2 config volume to 7+2 volume. You can not change the > *configuration* of an existing volume. > You can just add bricks in multiple to increase the storage capacity. > > > Yes and this is the worst thing in gluster: the almost zero flexibility > > Bigger the cluster, higher the cost to maintain it or expand it. > At least in case of EC it is with good reason. If you want to change volume's configuration from 6+2->7+2 you have to compute the encoding again and place different data on the resulting 9 bricks. Which has to be done for all files. It is better to just create a new volume with 7+2 and just copy the files on to this volume and remove the original files on volume with 6+2. > If you start with a 6:2 by using commodity hardware, you are screwed, your > next upgrade will be 8 servers with 1 disk/brick each. > Not true. > > Yes, gluster doesn't make use of any metadata server, but I really prefer > to add 2 metadata server and 1 storage server at once when needed than > avoid metadata servers but being forced to add a bounch of servers every > time > > More servers means more power cost, more hardware that could fails and so > on. > > Let's assume a replica 3 cluster. > If I need to add 2tb more, I have to add 3 servers with 2tb on each server. > Ceph, Lizard, Moose and others allow adding a single server/disk and then > they rebalance data aroud by freeing up the used space adding the new disk. > Didn't understand this math. If you want to add 2TB capacity to a volume that is 3-way replicated, you essentially need to add 6TB in whatever solution you have. At least 6TB with a single server. Which you can do even with Gluster. > > I thought that this lack of flexibility was addressed is some way in > latest version... > I think we had this discussion last July[1] with you that we can simulate the same things other storage solutions with metadata do by doing replace-bricks and rebalance. If you have a new server with 8 bricks then we can add a single server and make sure things are rebalanced with 6+2. Please note it is better to use data-bricks that is power of 2 like 4+2/8+2/16+4 etc than 6+2. Are you suggesting this process to be easier through commands, rather than for administrators to figure out how to place the data? [1] http://lists.gluster.org/pipermail/gluster-users/2016-July/027431.html > _______________________________________________ > Gluster-users mailing list > [email protected] > http://lists.gluster.org/mailman/listinfo/gluster-users > -- Pranith
_______________________________________________ Gluster-users mailing list [email protected] http://lists.gluster.org/mailman/listinfo/gluster-users
