I'm trying to add a cache pool of two SSD drives to my aging unRAID tower. I'm using a Supermicro C2SEE board, and have maxed out the 6 SATA connectors with Parity + 5 data drives. I came across this Silverstone ECM20 adapter onto which I can mount 2 M.2 SSD drives. It is installed in a PCI-E x4 slot, and one of the mounted M.2 drives interfaces directly with the PCI-E slot and the other requires a SATA connection (and is therefore not usable for me, as I have no more SATA connectors left). So I will need one adapter per drive for my situation.

 

However, I'm not sure whether my available PCI-E slots will let me take advantage of this adapter and M.2 drives, and I'm quite confused by the PCI-E slot terminology. The board has one PCI-E x1 slot, which is clearly too small. It also has a "PCI-E Gen2 x16" slot and a "PCI-E x4 on x16" slot. I understand that the x16 in both cases refers to the length of the slot. So I'd like to install one M.2 SSD in each of these slots.

 

From my Googling, it seems that physically I can install the adapter in both of the x16 slots, since I just need the slot to be at least x4 in size. But how is the speed affected? I'm guessing that the PCI-E x4 on x16 slot will be fast enough. But will the PCI-E Gen2 x16 slot be fast enough? I don't need the SSDs to be as fast as possible; I'd just like them to at least feel like SSD-speed 

The PCIe gen2 x16 slot has plenty of bandwidth, max theoretical is up to 8000MB/s.

 

The PCIe x4 on x16 on the other hand will have to share the DMI bandwidth (up to 1000MB/s) with the onboard SATA ports, since you plan to use the SSDs for cache it’s not really an issue, but you could notice some performance degradation during parity checks, as in my experience DMI 1.0 max real world bandwidth is ~720MB/s, this will be shared by all SATA ports plus the cache disk on that slot.

 

Thanks, johnnie.black, that's exactly what I needed to know!

I've been looking into these lately - although I'm not sure how reliable they are.

 

http://www.newegg.com/Product/Product.aspx?Item=9SIA1JM2CZ0247&cm_re=sedna-_-9SIA1JM2CZ0247-_-Product

 

I have 2x M.2 SSD's salvaged from work laying around that I want to use in my cache for a future build and I've been looking into alternatives such as this one. I know they won't get the full benefit of M.2 speed, but I don't really care at this point. Does anyone have any other ides? I'll have one PCI Express x4 and one x1 to work with.

 

Edit: there is also the option of getting another AOC-SASLP-MV8 and 2 of these:

 

http://www.newegg.com/Product/Product.aspx?Item=9SIA24G2HZ0865&cm_re=startech_m.2_2.5-_-17-707-378-_-Product

 

which would be cheaper and give me much more expandability down the line.