Dual Cache Drives PCIe Lanes Usage

[Iceman24]

I'm about ready to order parts for my unRAID build, but had a question regarding PCIe lanes usage with dual M.2 NVMe cache drives. I'm looking at the Supermicro X11SCH-F motherboard which has 2 M.2 NVMe ports with PCIe 3.0 x4 for each slot. No mentioned sharing of anything. I won't have more than 2 USB drives plugged in and 3 HDD's at max most likely. Perhaps a GPU card for passthrough at a later date, but not planned at this time.

 

From what I read, SB has its own PCIe lanes, so that seems okay from that perspective. The only thing I'm really wondering as I am figuring the 2 M.2 slots support full speed with each having a drive in them, is the upstream of the C246 chipset to the CPU is only x4, not the full x24 the chipset offers. Does this matter for M.2 cache drives? They will be RAID 1 if that matters.

[drdebian]

Whatever the board is doing, a single x4 lane should easily be able to handle your 2 SSDs at maximum speed. 

[Vr2Io]

All C246 downstream device will be share the upstream x4 link, i.e. HDD, LAN, USB ....

There are many report no matter single/dual NVMe, even direct connect to CPU PCIe also can't reach benchmark speed. Different NVMe also have different issue. Pls search on forum. I'm not means NVMe not good, it still the king of speed, just don't expect the result by simple calculation.

Edited July 8, 2019 by Benson

[Iceman24]

Thanks. Was there a specific issue(s) with NVMe? I've done some research. Nothing stood out to me regarding any NVMe issues.

[Vr2Io]

For example

 

 

Edited July 8, 2019 by Benson

[Iceman24]

For example
 
 

Lol. Funny you picked that one. I was last poster in that thread. I figured that it may have had to do with using an add-in card for connecting M.2 drives. Motherboard I'm looking at has them built-in. I read similar post as well that referenced only issues with M.2 that used add-in card instead of built-in slot.

[Iceman24]

Reading through that thread more carefully has me thinking I should reevaluate my SSD choice, but unsure which to get. Samsung ones are way more expensive, so I didn't want to just say forget any others and pay that much more times 2.

[Vr2Io]

3 minutes ago, Iceman24 said:

Lol. Funny you picked that one. I was last poster in that thread. I figured that it may have had to do with using an add-in card for connecting M.2 drives. Motherboard I'm looking at has them built-in. I read similar post as well that referenced only issues with M.2 that used add-in card instead of built-in slot.

😆, There are no different between add-in card and mainboard build-in. Pls well planning and research.

[Iceman24]

, There are no different between add-in card and mainboard build-in. Pls well planning and research.

Thanks. Are there in particular NVMe drives that are free of issues? I've also read in one place that performance is barely different compared to SATA due to sequential reads/writes not really being used, but mostly random, which has similar speeds. SSD's have become cheap enough that I wanted the latest and greatest for minor cost difference, plus more clean install in case.

[Vr2Io]

May be Samsung still the best, most NVMe work well with Unraid, just some specific case will got trouble.

I just try Plextor M8peg as simple cache storage use and no any problem, but finally I take it out for Windows machine, because it utilize it better.

Edited July 8, 2019 by Benson