Hi, Yes, currently H2 does not offer real scalability (no scalable writes or reads) beyond one process. The current clustering feature is very limited. I do think about adding sharding and replication (basically what MongoDB is doing) on the storage level (MVStore). But this will take a while (not this year, and I'm not sure about next year).
Regards, Thomas On Tue, Nov 12, 2013 at 4:48 PM, Adam McMahon <a...@cs.miami.edu> wrote: > Thomas, > > This sounds like a good plan, and I realize there is a strong priority for > the MVStore. > > When I look at the other major DBs: MySQL, Mongo, etc. They all seem to > have a feature to allow replication for faster reads. While H2 may fit a > different market than these other DBs, but it would be nice to have have > replication performance boosts. > > For my particular use case, I use H2 for rest/web services (similar to how > many people use MySQL/Mongo). Here is my scalability flow/plan: > > 1) For for most services, I simply embed H2 in the web server - this works > great, simple and super fast. > 2) If the volume on the services gets too high and heaps sizes are too > big, H2 is split to client/server mode on the same CPU > 3) If the volume continues to increase, then H2 can be put on a dedicated > server. > 4) But what next? there is no way to scale higher via a cluster. Because > of this fact, individuals may pick another DB (which is fine if H2 does not > want to compete in this space). > > Another potential problem of H2 scalability is that of large > garabage collection pauses on large heap sizes. This is not a problem with > H2, but a problem with Java in general. If someone has a dedicated H2 > server and wants to scale higher, they may not get much more power by > increasing H2's cache, as I imagine it will (like most Java apps) run into > problems with large heap sizes. So, really H2 will likely cap its > scalabilty on a commodity computer with about 4 GB of ram (if the user is > concerned with having low latency for requests). > > Cluster replication might just save the day here. When volume of requests > or heap sizes get too big, replication can be used to scale horizontally. > But then again, perhaps I am looking at H2 to do something that it is not > intended to do, and where another DB may be a better fit, which is fine. > > Thanks for your hard work on this great product. > > -Adam > > > > On Tuesday, November 12, 2013 8:39:55 AM UTC-5, Thomas Mueller wrote: > >> Hi, >> >> I'm afraid the current implementation does not support it. Of course this >> could be changed, actually I guess it would be relatively easy to remove >> the check. >> >> At some point I think it's better to re-implement clustering. But first >> my priority is to work on the new storage engine (the MVStore), I plan to >> use this mechanism as the base for the new clustering. >> >> Regards, >> Thomas >> Am 12.11.2013 02:40 schrieb "Adam McMahon" <ad...@cs.miami.edu>: >> >>> H2 Group, >>> >>> I am checking out the clustering features of H2. I know that the >>> clustering features are fairly barebones. I am interested in >>> using clusters/replication for increased performance, as opposed to simply >>> having a failsafe DB online (which is also a good thing :). >>> >>> In the past, using MySQL replication, I would send write queries to the >>> master (which would eventually be propogated), and then I would load >>> balance between the master/slaves for read queries. I would do this at the >>> application level by simply changing the JDBC url depending on if the SQL >>> was a write or a read. The slaves might be a little behind the master, but >>> that was fine for many of my queries. >>> >>> I know that load balancing is not a built in feature to H2 clustering, >>> but I figured I may be able to accomplish it at the application level using >>> something like the above. However, it seems that I am not able to do so, >>> as client connections to an individual server with in a cluster are >>> rejected. I appears we can only connect to using the server list url. >>> >>> My question: is there any way to load balance reads across a slave? >>> >>> Thanks, -Adam >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "H2 Database" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to h2-database...@googlegroups.com. >>> To post to this group, send email to h2-da...@googlegroups.com. >>> >>> Visit this group at http://groups.google.com/group/h2-database. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >> -- > You received this message because you are subscribed to the Google Groups > "H2 Database" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to h2-database+unsubscr...@googlegroups.com. > To post to this group, send email to h2-database@googlegroups.com. > Visit this group at http://groups.google.com/group/h2-database. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "H2 Database" group. 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