I like #1 if possible. Of course, if the LFS is empty, then the new default should be 4k.
On Tue, Aug 15, 2017 at 12:01 PM, Ivan Rakov <ivan.glu...@gmail.com> wrote: > Guys, > > We have benchmarked how checkpoint write speed on SSD disk depends on > various parameters. It became absolutely obvious that using 4K pages in > durable memory instead of 2K brings considerable, significant speed-up. I > think, we must set 4K as default page size. > Ticket with detailed explanation: https://issues.apache.org/jira > /browse/IGNITE-5884 > Spoiler: it depends on write order and alignment, but writing 4K is at > least *3x faster* than writing 2K when other parameters are the same. > > The question is backwards compatibility. If pageSize is not explicitly set > in user configuration, attempt to start "4k default" Ignite node from "2k > default" LFS files will fail with exception: > > class org.apache.ignite.IgniteCheckedException: Failed to verify store >> file (invalid page size) [expectedPageSize=4096, filePageSize=2048] >> at org.apache.ignite.internal.processors.cache.persistence.file >> .FilePageStore.checkFile(FilePageStore.java:206) >> at org.apache.ignite.internal.processors.cache.persistence.file >> .FilePageStore.init(FilePageStore.java:416) >> at org.apache.ignite.internal.processors.cache.persistence.file >> .FilePageStore.read(FilePageStore.java:315) >> at org.apache.ignite.internal.processors.cache.persistence.file >> .FilePageStoreManager.read(FilePageStoreManager.java:287) >> at org.apache.ignite.internal.processors.cache.persistence.file >> .FilePageStoreManager.read(FilePageStoreManager.java:272) >> at org.apache.ignite.internal.processors.cache.persistence.page >> mem.PageMemoryImpl.acquirePage(PageMemoryImpl.java:569) >> at org.apache.ignite.internal.processors.cache.persistence.page >> mem.PageMemoryImpl.acquirePage(PageMemoryImpl.java:487) >> at org.apache.ignite.internal.processors.cache.persistence.Grid >> CacheOffheapManager.getOrAllocateCacheMetas(GridCacheOffheap >> Manager.java:515) >> at org.apache.ignite.internal.processors.cache.persistence.Grid >> CacheOffheapManager.initDataStructures(GridCacheOffheapManager.java:86) >> at org.apache.ignite.internal.processors.cache.IgniteCacheOffhe >> apManagerImpl.start(IgniteCacheOffheapManagerImpl.java:139) >> at org.apache.ignite.internal.processors.cache.CacheGroupContex >> t.start(CacheGroupContext.java:868) >> > > I think, we have two options here: > > 1) Obvious and safe - provide silent backwards compatibility. We can > implement a task which will find any LFS file, check its pageSize and use > it as default. > 2) Less user-friendly, but in my opinion still better option - crash node, > but make error message more informative. We'll let user know that default > pageSize was changed to 4k due to discovered performance boost on most > UNIX-based enviroments with SSD (which is for sure most popular enviroment > among users), and recommend user to migrate to 4K-page LFS. If user still > wants to work with 2k pages, he can always set it explicitly in > MemoryConfiguration and start node. > > Thoughts? > > -- > Best Regards, > Ivan Rakov > >
