Optane - now SSD on a DIMM

By: Maynard Handley (name99.delete@this.name99.org), April 19, 2019 4:11 pm
Room: Moderated Discussions
Howard Chu (hyc.delete@this.symas.com) on April 19, 2019 11:37 am wrote:
> mpx (mpx.delete@this.nomail.pl) on April 17, 2019 2:12 am wrote:
> >
> > Some database engines already use NVDIMM by using memcopy rather
> > than file system access to acces persistent data on NVDIMM.
> >
> > https://docs.microsoft.com/pl-pl/sql/linux/sql-server-linux-configure-pmem?view=sqlallproducts-allversions
> >
> With LMDB we don't even need the memcopy.
> http://www.lmdb.tech/bench/optanessd/
> I'm gonna have to ping our Intel guy again and see about permission to publish our Optane DIMM test
> results. By now the embargo must've expired, since the DIMMS are now commercially available.

I suspect the MS talk of "memcopy" is not literal, it's trying to get the idea across.
MS are as aware as anyone (and have certainly published plenty) that you CANNOT simply memcopy globs of data to your persistent memory safely. At the very least, for safety, you need to interleave writes with persistence ordering primitives;
and if you want optimal performance you also need to restructure (or at least reparameterize) your data structures to match the new minimum write size (which we used to be told was byte, then we kinda assumed was a cache line, and now we're being told is 256 bytes). If you have byte (or at least 8 byte) granularity, you can think about things like a database structured like in-RAM data-structures, and MS did some work on that. Of course once you're at 256 bytes, maybe your best bet is to stick with file-system data structures, just resize things like the B-tree blocks to 256 bytes rather than 4K?
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TopicPosted ByDate
Optane DC Motherboards?anonymous22019/04/07 11:22 AM
  Optane DC Motherboards?Adrian2019/04/07 12:05 PM
    thanksanonymous22019/04/08 09:21 AM
      Optane - now SSD on a DIMMNoSpammer2019/04/16 06:11 AM
        Optane - now SSD on a DIMMwumpus2019/04/16 07:55 AM
          Optane - now SSD on a DIMMmpx2019/04/17 02:12 AM
            Optane - now SSD on a DIMMHoward Chu2019/04/19 11:37 AM
              Optane - now SSD on a DIMMMaynard Handley2019/04/19 04:11 PM
        Optane - now SSD on a DIMMDaniel B2019/04/18 02:00 AM
          Optane - now SSD on a DIMMHoward Chu2019/04/19 11:35 AM
          Optane - now SSD on a DIMMNoSpammer2019/04/23 02:37 AM
            Optane - now SSD on a DIMMDaniel B2019/04/23 04:56 AM
            Optane - now SSD on a DIMMMark Roulo2019/04/23 07:46 AM
              Optane - now SSD on a DIMMWes Felter2019/04/23 07:55 PM
                Optane - now SSD on a DIMMMark Roulo2019/04/24 06:52 AM
                  Optane - now SSD on a DIMMEtienne2019/04/25 01:11 AM
                    Why not copy to fast SRAM?Mark Roulo2019/04/25 07:24 AM
                      Why not copy to fast SRAM?Etienne2019/04/26 01:55 AM
  Optane DC Motherboards?Daniel B2019/04/09 10:42 AM
    Optane DC Motherboards?wumpus2019/04/09 10:47 AM
      Optane DC Motherboards?Daniel B2019/04/09 03:49 PM
    Optane DC Motherboards?anyone2019/04/10 06:42 AM
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