I got a 2x M.2 board from them. The card did not work. One port shows pcie errors. Their tech support is awful, keeping asking from the same information.Any recommendations? I saw this one from Amfeltec but I'd love to hear if anyone has experience with a particular model. I'm using an EPYC server board and just want to use the 4 NVMe drives as a cache tier (no RAID).
PCI Express Gen 3 Carrier Board for 4 M.2 SSD modules - Amfeltec
I am indeed NOT sure. I was not aware that was the case.Are you sure? I thought all the raid calculation/verification for data integrity happens on the host cpu and would require data from all devices in the logical volume.
Did you mean the same as a two drive RAID1?I read somewhere once aeons ago that btrfs didn't stripe reads from a RAID1 or RAID10 device - I don't know if that's still the case (I would hope not) but last I looked the 4-drive RAID10 had the same read speed as a 2-drive RAID0.
Its probably me who's info is wrong. I didn't realize RAID10 reads were off all 4 disks. I though it just read off each striped mirror but not all 4 drives.Nope, two-drive RAID0. Like I said my info is probably out of date but when I last checked btrfs didn't seem to stripe reads very well, if at all.
I agree, workload wise I'm not worried about the PCIe x8 limiting me. I wish there was another x8 option other than the SM since I don't need the PLX chip.It depends on the implementation, you could quite easily have a RAID10 that only ever read off one drive if you wanted to (although that'd be rather stupid). But the thrust of things was that btrfs certainly didn't use this particular optimisation - not that I think it'll make a significant difference for your workload.
Regardless of the optimisation though, writes would always need to go to all discs and reads can conceivably come from all discs so ideally your PCIe bandwidth would be able to sustain maximum seq read of all devices at once. With btrfs this probably won't be an issue but given your PCIe constraints it's not one I'd worry about anyway.
Asus seemed to give up on their M2 cards pretty early. ASRock did their own take on this called the Ultra Quad and that's still available in the UK at least, although at prices that make it cost the same as the Supermicro AOC-SHG3-4M2P-O with PLX chip (£140 on amazon UK for the Ultra Quad vs. £135 for the AOC-SHG3-4M2P at LambdaTek).
Somewhat surprised they aren't more common stateside...