Optane - now SSD on a DIMM

By: Howard Chu (hyc.delete@this.symas.com), April 19, 2019 11:35 am
Room: Moderated Discussions
Daniel B (fejenagy.delete@this.gmail.com) on April 18, 2019 2:00 am wrote:
> NoSpammer (no.delete@this.spam.com) on April 16, 2019 6:11 am wrote:
> > anonymous2 (anonymous2.delete@this.example.com) on April 8, 2019 9:21 am wrote:
> > > Thanks.
> > >
> > > My read of all that is Optace DC is mostly a high-end chipset/CPU feature and still some ways
> > > off, not something you will see in desktops or even smaller workstation for quite some time.
> >
> > Maybe right now it seems high-end, but later on it could be useful for any app that needs high-speed
> > logging, write-ahead logging, transactional consistency, checkpointing, recovery etc. You can
> > count here pretty much all database related stuff, financial software, any high-speed transactions,
> > backend loggers, some industrial data collection, advanced file systems...
> >
> > What I find ridiculous is that after all this brouhaha about Xpoint replacing
> > RAM we've got what is essentially SSD on a DIMM with 256-byte blocks plus significant
> > ECC overhead (11 chips LOL) plus RAM for remapping/buffering/whatever.
> >
> > On the other hand I give Intel thumbs up for making this work despite the obstacles.
> > It's still great to have a SSD which can receive small data chunks in DDR4 bursts.
>
> I'm not sure how your judgment follows from your own assessment : it works. Intel also published
> guidelines on DRAM-Optane ratios for different targets (performance vs. capacity) and what to
> expect relative to raw DRAM performance. Initial data I've seen is encouraging in that you get
> 90%+ of performance on average, but where app performance on balance will improve due to larger
> data sets in memory. I'm sure there will be corner cases when it will make applications struggle.
> But by and large it seems like a good trade off, memory tiering that is.

As a new memory tier between DRAM and 2ndary storage, it makes sense. Currently that's not really how Intel is pitching it though, they're pushing it as either a block device for hosting a filesystem - i.e., a glorified RAMdisk, or as a RAM emulator.

I tested this stuff pretty extensively over several weeks last summer and none of the scenarios Intel was interested in actually made any sense. I had to construct new scenarios for the purpose instead.

The only thing that makes sense is for this to be a persistent cache in front of SSD/HDD storage, and currently there is no OS support for such a thing. Although at least in Linux, there are a number of dynamically loadable cache management modules (like bcache, etc.) that could be easily modified for the purpose.
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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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