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Its unfortunate how U.2 does not receive much attention. How much M.2 devices can you probably fit into curent workstation/server motherboards? 3? U.2. takes pl

Its unfortunate how U.2 does not receive much attention. How much M.2 devices can you probably fit into curent workstation/server motherboards? 3? U.2. takes place of SATA for being a dedicated connection to multiple storage devices and can fit so much more in same chassis. If we need some sort of new-gen ssd raid, the unweildiness of m.2 mounting won't gonna cut it. The u2 benefits, compared to m2 mentioned on wikipedia seems to miss the point - u.2 is meant to be important in server space where you can have 12 drives per 1U, all with frontal/top load. all these cards we have with m.2 are not meant and cannot be operated at storage-system scale.

homero 8y ago
What about Intel didn't make enough PCIe lanes available in consumer chipsets to run enough U.2 drives to be attractive. Whether U.2 or M.2, Intel was always only going to give you one or two.
- altmind 8y ago
  Yes, that's also a problem. Yet, even intel on prosumer grade x299 had 44 cpu+24 slower chipset lanes where each nvme need 4x. AMD, otoh have EPYCs with 128 total lanes. Maybe demand would've lead intel into making changes to their server lineup.
  - masklinn 8y ago
    > Maybe demand would've lead intel into making changes to their server lineup. Competition might, but it doesn't look like Zen's popular enough (Zen provides 24 lanes at the low end, 64 on HEDT, and as you noted 128 on EPYC, IIRC Intel's entire consumer lines is a flat 16).
    - dogma1138 8y ago
      Zen doesn’t really provide 24 lanes on the low end any more than Intel does “20” as both provide only 16 lanes for general purpose use, in Zen desktop 4 are reserved for the CPU to Chipset bus and 4 more are reserved for the SoC I/O.
    - Aengeuad 8y ago
      Intel does provide 28/40 lanes on HEDT, at least starting with x99. I'm not sure about previous generations. The 16/20 lanes is for general consumer CPUs.
CoolGuySteve 8y ago
There are PCIe x16 cards that let you plug in 4 m.2 SSDs, so theoretically you could make a system with 4 times as many SSDs as you have x16 slots. The overhead of RAID might nullify the performance gains of NVMe though, as this benchmark of 3 NVMe drives shows: https://www.pcper.com/reviews/Storage/Triple-M2-Samsung-950-Pro-Z170-PCIe-NVMe-RAID-Tested-Why-So-Snappy/Preliminary-Resul https://www.pcper.com/reviews/Storage/Triple-M2-Samsung-950-... It delivers similar performance to a SATA SSD array I built years ago for bandwidth (not sure about IOPS though).
- altmind 8y ago
  its true there are 16X=>4x4 cards, but these need pci bifurcation. recent intel-based HP g9 servers that I tested, do not have bifurcation support, even with the latest firmware, unlike AMD cpus/chipsets.

homero 8y ago

What about Intel didn't make enough PCIe lanes available in consumer chipsets to run enough U.2 drives to be attractive. Whether U.2 or M.2, Intel was always only going to give you one or two.

altmind 8y ago
Yes, that's also a problem. Yet, even intel on prosumer grade x299 had 44 cpu+24 slower chipset lanes where each nvme need 4x. AMD, otoh have EPYCs with 128 total lanes. Maybe demand would've lead intel into making changes to their server lineup.
- masklinn 8y ago
  > Maybe demand would've lead intel into making changes to their server lineup. Competition might, but it doesn't look like Zen's popular enough (Zen provides 24 lanes at the low end, 64 on HEDT, and as you noted 128 on EPYC, IIRC Intel's entire consumer lines is a flat 16).
  - dogma1138 8y ago
    Zen doesn’t really provide 24 lanes on the low end any more than Intel does “20” as both provide only 16 lanes for general purpose use, in Zen desktop 4 are reserved for the CPU to Chipset bus and 4 more are reserved for the SoC I/O.
  - Aengeuad 8y ago
    Intel does provide 28/40 lanes on HEDT, at least starting with x99. I'm not sure about previous generations. The 16/20 lanes is for general consumer CPUs.

CoolGuySteve 8y ago

There are PCIe x16 cards that let you plug in 4 m.2 SSDs, so theoretically you could make a system with 4 times as many SSDs as you have x16 slots. The overhead of RAID might nullify the performance gains of NVMe though, as this benchmark of 3 NVMe drives shows: https://www.pcper.com/reviews/Storage/Triple-M2-Samsung-950-Pro-Z170-PCIe-NVMe-RAID-Tested-Why-So-Snappy/Preliminary-Resul https://www.pcper.com/reviews/Storage/Triple-M2-Samsung-950-... It delivers similar performance to a SATA SSD array I built years ago for bandwidth (not sure about IOPS though).

altmind 8y ago
its true there are 16X=>4x4 cards, but these need pci bifurcation. recent intel-based HP g9 servers that I tested, do not have bifurcation support, even with the latest firmware, unlike AMD cpus/chipsets.