Using a 24-port backplane for 8 SATA, 8 SAS, and 8 U.2

code_gs

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With the memory model I'm using for my server, I need an array of 8 SATA3, SAS3, and U.2 drives. The SATA drives will be JBOD, SAS in RAID 0 thru a card, and the u.2s in software RAID 0. The BPN-SAS3-846EL1-N8 seems to fit this need perfectly (and fit in my CSE-847), but I just wanted to make sure, will this support mixing SAS and SATA drives with no speed loss? Will a cable like Amazon.com: Internal Mini SAS HD SFF-8643 to 4 SATA Internal Cables 1 Meter : Electronics work for connecting the SATA ports on the mobo to the Mini SAS connectors on the backplane?
 

MiniKnight

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You shouldn't have issues mixing drives but that looks like it is an expander backplane so that may limit you.
 

i386

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You shouldn't have issues mixing drives but that looks like it is an expander backplane so that may limit you.
The sas/sata ports are from the expander, the 8 pcie ports are "straight through" ports (similar to tq backplanes).
 

code_gs

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You shouldn't have issues mixing drives but that looks like it is an expander backplane so that may limit you.
If I only use 4/6 ports on the two lanes that don't have NVMe ports, will my speed still be limited or will I get full throughput? What about on the lane that shares 2 NVMe ports?
 

Sean Ho

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the 8 NVMe-capable bays are basically electrically separate from the 16 other bays, even though two of those NVMe-capable bays are located in the same column as non-NVMe bays. You can use any of those 8 NVMe-capable bays for your U.2s. Each one is straight-through, doesn't go through the expander.

However, if you were planning on driving some of the 16 expander bays with a RAID card and some with onboard SATA, I don't think that'll work. There's only one 8643 on the backplane, and that feeds the expander to all 16 bays. If you're ok with software raid on everything, you could drive the backplane with a SAS3 HBA and mix SATA3 and SAS3 drives. All drives would sync at their respective full speeds. (Caution about RZAT/DRAT for TRIMming SATA SSDs via SAS HBA.)
 
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code_gs

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However, if you were planning on driving some of the 16 expander bays with a RAID card and some with onboard SATA, I don't think that'll work. There's only one 8643 on the backplane, and that feeds the expander to all 16 bays.
How about the BPN-SAS3-846EL2? Ditching the NVMes, will 4*2 SAS3 on the first two lanes (coming from a Broadcom SAS3008) and 4*2 SATA on the other two (coming directly from the mobo) work, or do I still need another HBA?
 

BlueFox

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SAS expander backplanes will only work with SAS HBAs, not your motherboard's SATA ports. You also will only be able to use a single HBA (zoning and dual-porting aside). With that backplane, you would run all 24 drives of the 3008. You would be bandwidth limited to the 8 lanes, but at 9.6GB/s, doubt that's a problem.
 
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Sean Ho

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If you wanted to run some bays off a SAS HBA and some off motherboard SATA ports, a TQ backplane would work: one 7-pin SATA port per bay, no expander. Whether the bay supports SAS3 / SAS2 / SATA is up to whatever you connect it to. TQ would not be able to do U.2, though.
 

code_gs

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If you wanted to run some bays off a SAS HBA and some off motherboard SATA ports, a TQ backplane would work: one 7-pin SATA port per bay, no expander. Whether the bay supports SAS3 / SAS2 / SATA is up to whatever you connect it to. TQ would not be able to do U.2, though.
This seems like the way to go. Is it possible to physically "stack" 3 of these TQ backplanes in the front 24 bays, or will some tape be necessary?
 

code_gs

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How about an 846 tq backplane?
Perfect form factor and count but I'm still confused in general about the SATA ports on the back (on this and the SAS3-*TQs) - will these be able to carry 12gb/s? If they can, then what's the point of the SAS3-*TQ backplane line if the SAS-*TQ backplanes already support all that is needed?
 

gregsachs

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Perfect form factor and count but I'm still confused in general about the SATA ports on the back (on this and the SAS3-*TQs) - will these be able to carry 12gb/s? If they can, then what's the point of the SAS3-*TQ backplane line if the SAS-*TQ backplanes already support all that is needed?
My understanding is that it is a case of "certification/support". The -sas TQ backplane is only certified for sas-1, but it is straight through wiring from the input to the drive, so....
 

Sean Ho

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Yes, the SAS-TQ backplane can carry 12Gbps SAS3 signalling. If you only have 8x SAS3 drives, an -8i SAS3 HBA and a pair of forward breakout cables would be sufficient. Most SAS3 HBAs use 8643; some use 8087; a very few have 7-pin SATA-format connectors already broken out. So you'd use, e.g., 1x8643-to-4xSATA forward breakout cables between the HBA and the TQ backplane.

When you get more SAS3 drives, you'd add either another HBA or an expander, plus more breakout cables. Cabling can get to be a bit of a pain (not to mention blocking airflow), which is one of the advantages of the backplanes with builtin expander.
 
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