I suppose it is about Ignite Page Memory pages defragmentation. We can get 100 allocated pages each of which becomes only e.g. 50% filled after removal some entries. But they will occupy a space for 100 pages on a hard drive.
пт, 28 дек. 2018 г. в 20:45, Denis Magda <dma...@apache.org>: > > Shouldn't the OS care of defragmentation? What we need to do is to give a > way to remove stale data and "release" the allocated space somehow through > the tools, MBeans or API methods. > > -- > Denis > > > On Fri, Dec 28, 2018 at 6:24 AM Vladimir Ozerov <voze...@gridgain.com> > wrote: > > > Hi Vyacheslav, > > > > AFAIK this is not implemented. Shrinking/defragmentation is important > > optimization. Not only because it releases free space, but also because it > > decreases total number of pages. But is it not very easy to implement, as > > you have to both reshuffle data entries and index entries, maintaining > > consistency for concurrent reads and updates at the same time. Or > > alternatively we can think of offline defragmentation. It will be easier to > > implement and faster, but concurrent operations will be prohibited. > > > > On Fri, Dec 28, 2018 at 4:08 PM Vyacheslav Daradur <daradu...@gmail.com> > > wrote: > > > > > Igniters, we have faced with the following problem on one of our > > > deployments. > > > > > > Let's imagine that we have used IgniteCache with enabled PDS during the > > > time: > > > - hardware disc space has been occupied during growing up of an amount > > > of data, e.g. 100Gb; > > > - then, we removed non-actual data, e.g 50Gb, which became useless for > > us; > > > - disc space stopped growing up with new data, but it was not > > > released, and still took 100Gb, instead of expected 50Gb; > > > > > > Another use case: > > > - a user extracts data from IgniteCache to store it in separate > > > IgniteCache or another store; > > > - disc still is occupied and the user is not able to store data in the > > > different cache at the same cluster because of disc limitation; > > > > > > How can we help the user to free up the disc space, if an amount of > > > data in IgniteCache has been reduced many times and will not be > > > increased in the nearest future? > > > > > > AFAIK, we have mechanics of reusing memory pages, that allows us to > > > use pages which have been allocated and stored removed data for > > > storing new data. > > > Are there any chances to shrink data and free up space on disc (with > > > defragmentation if possible)? > > > > > > -- > > > Best Regards, Vyacheslav D. > > > > > -- Best regards, Ivan Pavlukhin
