4 ms·
I don't quite understand. Does this act like a stick of memory or an SSD? Is it just using the memory controller as a super fast parallel bus? If it does act li
by zrail 12y ago
I don't quite understand. Does this act like a stick of memory or an SSD? Is it just using the memory controller as a super fast parallel bus? If it does act like normal memory, what happens at reboot?
- toyg 12y ago> Does this act like a stick of memory or an SSD? Like an SSD. > Is it just using the memory controller as a super fast parallel bus? Afaik, it's this.
- jpgvm 12y agoTechnically it acts like memory. The dev kit comes with a device driver that makes it look like a block device though, which would be analogous to something like NVMe.
- solarexplorer 12y agoIIRC a single DDR3 slot can address max 8GBytes. So the driver will have to map the 400GB Flash into this window.
- Dylan16807 12y agoDDR3 supports 8gbit chips and you can shove 16 onto one DIMM, so 16GB. But that leaves 3 address lines unused for column select. Theoretically they could make a 64GB or 128GB board. Also LRDIMMs can go up to at least 64GB. DDR4 directly supports 512GB, and also throws away three potential column address bits.
- jhallenworld 12y agoWell at the interface level it has to look like memory since it's attached to a memory bus. But that does not mean it looks like a single large DIMM. There is no way in the DRAM protocol to delay a transaction while data is read from the flash chips into the buffer, so you need a protocol on top of the simple memory model. "nvDIMMs" on the other hand do look like and are as fast as plain memory. Disadvantage is that they are not big.
- deleted 12y ago[deleted]
- gnufied 12y agoAnswer is there in FAQ. Written data is not lost on reboot, so basically you can mount it as a `ramdisk` partition and use that as data directory for your database. I have used this approach in past to speed up large test suite of a web application, except it required restoring from some sort of backup on reboot. Which won't be necessary in this case.
- achille2 12y agoDoes this mean you won't have traditional memory available at all (outside of L1-3 cache)? Or is it able to mix and match between real DDR3 memory and SSD?
- throwaway_yy2Di 12y agoIt doesn't look exceptionally parallel -- the throughput figures are similar to those in PCIe SSDs. 880 MB/s doesn't come close to saturating even a PCIe bus (4 GB/s, for v2 8x), let alone DDR3 (13 GB/s per channel).
- vidarh 12y agoI agree, it's not that fast I have 1U servers with lots of RAM slots. Fitting in a RAID 10 is easy enough even in a "modest" 1U server with space for 8 DDR3 slots. We have servers with up to at least 16 DDR3 slots. And in most servers these days, drives take up a massive amount of physical space. Being able to drop the drives and RAID controller has the potential of massively simplifying some server hardware.
- daveloyall 12y agoSpeculation: these SSD dimms will require more power and more cooling than the ordinary dimms.