Ben T (ben.delete@this.noemail.com) on July 22, 2022 10:02 pm wrote:
> > Do people here think the ideal public cloud infrastructure would be
> > a cluster in a box rather than a single symmetric multiprocessor
> > running virtual machines from multiple users? For example, imagine
> > a 1U chassis containing 12 processor chips and 12 hot-swap
> > 2.5” U.2 NVMe drives. Each processor chip could include:
> >
> > 8 performance CPU cores plus caches
> > interfaces to two 128-bit LPDDR DRAMs
> > 4 PCIe lanes to connect to one NVMe drive
> > a 10G ethernet connection
> >
> > If the minimum unit a cloud user could get is 8 cores, they would not
> > be sharing this chip with anyone else so the risk of data leakage
> > between users would be greatly reduced. If it is possible to combine
> > these processor units for bigger single tasks but still keep them
> > partitionable into independent units for small tasks, that would be even better.
>
> Here is one way to put 12 processor packages in a 1U server. To fit in a standard 19” rack, the width of
> the motherboard has to be at most 17” (43.18cm). To have a single row of processor packages across the
> width of the chassis, each processor package could be about 3.4cm wide with a .2cm gap between packages.
> A processor package containing two LPDDR5X DRAM packages would be rectangular with the processor die in the
> middle and an LPDDR5X DRAM package on two opposite sides of the processor die. An LPDDR5X DRAM package is
> 1.4cm x 1.4cm. Apple’s M1 Max die is 2.16cm x 1.99cm so this all fits comfortably in a 3.4cm wide package.
> The long side of the rectangular processor package would be parallel to the air flow in the chassis. An alternative
> would be to have two rows of six processor packages (P) with a big gap between each package in a row so that
> cool air can reach the row of packages farthest from the air intake, like this:
>
> P_P_P_P_P_P
> _P_P_P_P_P_P
>
> A reason to have 12 processor packages is that the number of 2.5” drives that fit across the front
> of a chassis is a multiple of 12 (12 in a 1U chassis, 24 in a 2U chassis). Less fan power is needed
> when the heat sources are spread out instead of concentrated in one or two processor sockets.
>
> Does this seem practical?


I don't see that 2.5" form factor drives should be a consideration. One of the M.2 NVMe devices would seem to be much better suited to such a device.

It should certainly be possible to fit a dozen of these in a pizza box. Consider the sizes of something like Nano- or Pico-ITX motherboards.