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Originally posted by zyxxel View PostExcept that SATA is very good for lower-power solutions. Most higher-end solutions requires special cooling for the SSD. You are seriously underestimating SATA - especially when using HDD that doesn't have the bandwidth to saturate SATA.
Its not like SSD in m.2 have to be the high end models there are some that are as low as 2 watts there ok they are not high speed SSD but they are still faster than old school hard-drives.
Reality i see a pcie m.2 slot with a known compatible sata m.2 4 port that can be put into it as a good solution. Because those needing really low power may be going for a low power and lower performing m.2 pcie ok this is still faster than your hdd and uses less total system power than a HDD.
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Originally posted by oiaohm View Post
Except this is not exactly true that is good for lower power solutions. m.2 has a power limit of 7watts per slot yes that is your m.2 pcie 4.0 m.2 has to be inside 7 watts. Its really easy to have a harddrive with sata controller exceeding 7watts. Remember most soc chips don't have a sata controller built in so you have to put a sata controller on board but a lot socs have pcie express bus built in.
Its not like SSD in m.2 have to be the high end models there are some that are as low as 2 watts there ok they are not high speed SSD but they are still faster than old school hard-drives.
Reality i see a pcie m.2 slot with a known compatible sata m.2 4 port that can be put into it as a good solution. Because those needing really low power may be going for a low power and lower performing m.2 pcie ok this is still faster than your hdd and uses less total system power than a HDD.
One problem with m.2 is that you power the drive using that interface - so the interface must be able to supply that power. With SATA, you can require a different source for the power. Another thing with SATA is that I can use 5 TB 2.5" drives. Or 16 TB 3.5" drives. A SBC with two 16 TB drives is a quite nice backup solution. In the end, the RPi isn't intended as a high-end product and the additional speed for PCIe shouldn't normally matter. Especially since lots of people buy based on benchmarks instead of actual need.
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Originally posted by zyxxel View PostI'm not really sure where you get your metric that most SOC doesn't have SATA built in. Quite a number of chips I have looked at for creating embedded products have had SATA integrated.
Originally posted by zyxxel View PostOne problem with m.2 is that you power the drive using that interface - so the interface must be able to supply that power. With SATA, you can require a different source for the power.
Originally posted by zyxxel View PostAnother thing with SATA is that I can use 5 TB 2.5" drives. Or 16 TB 3.5" drives. A SBC with two 16 TB drives is a quite nice backup solution.
7 watt m.2 pcie in theory someone could make a 8 port Sata card to go in that the other would be a 4 port Sata 3.0/2 port Sata Express combination solution.
Originally posted by zyxxel View PostIn the end, the RPi isn't intended as a high-end product and the additional speed for PCIe shouldn't normally matter. Especially since lots of people buy based on benchmarks instead of actual need.
m.2 pcie would allow supporting any one of the of the following combinations
1) 8x sata 3.0 drives, by controller in m.2
2) 2x sata express ports by controller on m.2 (yes that is 4 sata 3.0 drives or 2 sata express drives.. Because each sata express port gives 2 sata 3.0 ports when a sata express connection is not being used
3) 1x SAS port by controller on m.2 (that up to 16 SAS drives or 4 SATA drives)
4) 1x m.2 pcie nvme.
Of course breaking the m.2 out to a powered pcie port would allow going to 128 drives. All these options I listed allows building a quite decent NAS.
I am not looking at pcie for the extra speed I am looking at the pcie for the flexibility. 16 Tb harddrive on a robot that is one of the raspberry pi usage cases is not really suitable where a 1TB nvme by m.2 would be suitable right. Remember running a sata cable of the board will only give increased risk of failure in the robot case so a 2.5/3.5 inch sata nvme is not really that suitable for the robot case.
M.2 sata vs m.2 pcie. Both have 7watt power usage provide requirement. The m.2 pcie can be used to connect more types of drives so the more flexible usage option when you don't know how the product will be used..
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