Ivan Rakov reassigned IGNITE-5884:

    Assignee: Ivan Rakov

> Change default pageSize of page memory to 4KB
> ---------------------------------------------
>                 Key: IGNITE-5884
>                 URL: https://issues.apache.org/jira/browse/IGNITE-5884
>             Project: Ignite
>          Issue Type: Improvement
>          Components: persistence
>            Reporter: Ivan Rakov
>            Assignee: Ivan Rakov
>             Fix For: 2.2
>         Attachments: CpBenchmark.java, iostat.log, ssdlab.log
> Checkpoint write speed is suboptimal with default 2K page on most UNIX-driven 
> enviroments with SSD disk. There are several reasons for this:
> 1) Page size of linux page cache is 4k by default on most kernels (you can 
> check yours by "getconf PAGE_SIZE" command). With 2k random writes 
> vm.dirty_ratio threshold is reached two times faster than with 4k random 
> writes.
> 2) Most SSD manufacturers don't reveal actual disk page size, but they 
> recommend to write at least 4k at once. Also, 4k blocks are used during 
> benchmarking SSD random writes. 
> Related question: 
> https://superuser.com/questions/1168014/nvme-ssd-why-is-4k-writing-faster-than-reading
> Article by Emmanuel Goossaert describing why writing less than a page is 
> —Āounterproductive: 
> http://codecapsule.com/2014/02/12/coding-for-ssds-part-3-pages-blocks-and-the-flash-translation-layer/
> I've prepared a checkpoint emulation benchmark (code and results attached). 
> Run on production-level hardware (CentOS, 100 GB RAM, total LFS size is 
> 100GB, vm.dirty_ratio=10) showed that checkpointing with 4k pages is much 
> more efficient than with 2k.
> *Important: backwards compatibility must be ensured with LFS files created 
> with old 2k default page size.*

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