Hey everyone, I need a couple clarifications regarding pci-e slots.  My motherboard has two pci-e slots.  Primary is a v3.0 x16 slot, and the secondary is a v2.0 x16 slot, "running in x4 mode".  The part in quotations is what I'm having trouble with.  Does that mean, if I'm using a device in the primary slot, the secondary slot will only run in x4 mode?  Does it matter what type of device is plugged into the primary slot?

 

Here's my problem.  I'd like to install a video card for virtualization.  Right now, both of my pci-e slots are being used by 4-port SATA controllers.  I plan on consolidating them to a single SATA controller such as this supermicro card.  That would open up a pci-e slot for a video card.  However, I've read that supermicro card requires an x8 slot.  Almost all video cards I've found require an x16 slot.  On top of that, the supermicro card won't physically fit in my lower pci-e slot.  It'd have to be installed in the primary pci-e slot.  Does that mean that the remaining secondary slot will only run in x4 mode?  Is there an issue running a video card on that slot?

 

Sorry for the rambling of questions.  I'm hoping someone more knowledgeable can read through my confusion and set me straight.

 

Thanks in advance.

-Dave

Without knowing the exact model of the motherboard, what you've posted means that the secondary 2.0 x16 slot always runs in x4 mode.

 

The SAS2LP will physically fit into the x16 slot.  Of the two slots to choose from I'd definitely put it into the 2.0 x16 (running in x4) as if you are only using HDD's, the performance hit will be negligible.  The SAS2 does require a x8 slot - but only physically.  It doesn't care (nor do any other cards out there) what the slot is electrically - in this case x4

 

Like Squid said, but since I had finished my reply here goes.

 

Does that mean, if I'm using a device in the primary slot, the secondary slot will only run in x4 mode?

 

No, it means that any card in that slot will run at x4, regardless of there is one in the upper slot.

 

However, I've read that supermicro card requires an x8 slot.

 

The SAS2LP should work in the x4 slot, it would perform a better in the top slot because it would be using 8 lanes, besides the x4 slot shares the DMI link with the onboard SATA ports, so it's going to be slower during parity checks/syncs and disk rebuilds but it should work.

Without knowing the exact model of the motherboard, what you've posted means that the secondary 2.0 x16 slot always runs in x4 mode.

 

The SAS2LP will physically fit into the x16 slot.  Of the two slots to choose from I'd definitely put it into the 2.0 x16 (running in x4) as if you are only using HDD's, the performance hit will be negligible.  The SAS2 does require a x8 slot - but only physically.  It doesn't care (nor do any other cards out there) what the slot is electrically - in this case x4

 

Awesome, thanks.  I included a link to my motherboard in the op but it was subtle, sorry.  It's the ASRock H97M-Pro4.  I read a couple Amazon/Newegg reviews (with a grain of salt, of course) that stated the SAS2 didn't like being plugged into an x4 slot.  One reviewer said they had to plug it into their primary (x16) slot for the card to work.  That point is moot though, because I physically HAVE to plug the SAS2 card in the x16 slot, because it won't physically fit into the x4 slot (see picture below).  Maybe I can find a different card that isn't as long.  Is there any problem running that SAS2 card in the x16 slot, and a video card like this one in the x4 slot?  I don't need crazy performance out of the video card.  I'm not a gamer.  I just want something powerful enough to run dual 1080p monitors with relative ease.

 

The SAS2LP should work in the x4 slot, it would perform a better in the top slot because it would be using 8 lanes, besides the x4 slot shares the DMI link with the onboard SATA ports, so it's going to be slower during parity checks/syncs and disk rebuilds but it should work.

 

Great, thanks for the reply.  As long as I can use a video card in the x4 slot, maybe I won't have a problem.

As an aside, you might want to rip off all of those SDx labels from the drives and replace them instead with say the last 4 digits of the serial numbers, as there is no guarantee that Linux keeps the same SDx number from boot to boot.  In the case of a failed drive, unRaid always reports the serial number of the drive in question.

A graphics card like the one you linked should perform fine on the x4 slot, unless the board has some bios limitation when using that slot for the primary gpu.

As an aside, you might want to rip off all of those SDx labels from the drives and replace them instead with say the last 4 digits of the serial numbers, as there is no guarantee that Linux keeps the same SDx number from boot to boot.  In the case of a failed drive, unRaid always reports the serial number of the drive in question.

 

YEP!  Absolutely.  I meant to tear off those stupid labels when I had the case open last, and simply forgot.  Those tiny little factory tags have the full serial on them, so I'm covered.  I also have a Google Sheet that details what is where.

A graphics card like the one you linked should perform fine on the x4 slot, unless the board has some bios limitation when using that slot for the primary gpu.

 

Great to hear, thanks again.

@De1taE1even what case is that?

@De1taE1even what case is that?

 

It's the Fractal Design R4 case with this CaseLabs fan-base cage: http://www.caselabs-store.com/hdd-cage-assy-standard/