Single socket 12 bay SAS chassis?

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spikeb

New Member
Apr 28, 2021
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Anyone seen a 2U or 3U chassis for a single socket Epyc chassis with a SAS backplane for 12 3.5" drives?

Was hoping to build something with 6 drives (one ZFS vdev) and be able to add 6 later. Was hoping for a backplane so I could use a LSI 8i card and not have to worry about running cables to each drive.

Anything similar could work. Doesn't even necessarily be rack mount.
 

spikeb

New Member
Apr 28, 2021
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Looks nice, does have a 12 bay backplane, even with a 2x expander. The manual has a VERY limited list of compatible supermicro motherboards (2 Intel motherboard). Is a Supermicro single socket epyc board likely to fit? Be compatible with the power supply?
 

NablaSquaredG

Layer 1 Magician
Aug 17, 2020
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You can install any E-ATX or ATX mobo you like inside an 826, even from other manufacturers (Gigabyte, ASRock, whatever). Just remember that you need a breakout / splitter cable (CBL-0084L) for the front panel connection (LEDs, Power / Reset Switch) if you want to use a non-Supermicro motherboard.

Depending on the revision, the 826 chassis should either have a PDB-PT825-8824 or a PDB-PT826-8824. Both give you standard 24pin ATX + 2x EPS (you might need an extension, depending on the motherboard layout though)

Note: The 826 is available with a variety of Backplanes.
There are:
BPN-SAS-826A -> SAS 2 / SATA 3 (6G/s), has 3x SFF-8087 Ports NOTE: If you only use a standard SAS HBA with 2 ports (-> 8 drives), you will only be able to use 8 of the 12 ports. You either need an additional HBA, a reverse breakout cable for 4x SATA->SFF8087 or something similar

BPN-SAS-826TQ -> SAS 2 / SATA 3 (6G/S), has 12x SAS / SATA Ports. Situation is the same as for the BPN-SAS-826A

BPN-SAS2-826EL1 -> SAS 2 / SATA 3 (6G/s), has an expander on board -> No additional HBA needed, standard 2 port (actually 1 port) HBA is enough for all drives, 2 SFF 8087 Ports, but only one is an input (Means you're limited to 4*6G/s bandwidth in total)

BPN-SAS2-826EL2 -> SAS 2 / SATA 3 (6G/S), has TWO Expanders on board for redundancy. Crazy expensive, 4 SFF 8087 Ports, but only two are inputs and you're still limited to 4*6GBit/s bandwidth in total

BPN-SAS3-826EL1 -> SAS 3 / SATA 3 (SAS 12G/s, SATA still 6G/s), has an expander on board -> No additional HBA needed, standard 2 port HBA is enough. 4 SFF 8643 ports, 2 are inputs, 2 are for cascading. Note that this provides 4 times the total bandwidth compared with the SAS2 version (2 inputs instead of one and SAS3 instead of SAS2)

BPN-SAS3-826EL2 -> SAS 3 / SATA 3 (SAS 12G/s, SATA still 6G/s), has TWO expanders on board for redundancy. Crazy expensive. 8 SFF 8643 ports. Four are inputs, four are for cascading. Same total bandwidth as SAS3-826EL1

And now for the interesting ones:
BPN-SAS3-826EL1-N4 -> Hybrid Backplane. SAS 3 / SATA 3 (SAS 12G/s, SATA still 6G/s), BUT 4 of the slots are hybrid slots and can handle NVMe drives! Has an expander on board. Same game as for the SAS3-826EL1. Crazy expensive.

BPN-SAS3-826A-N4 -> Hybrid Backplane. SAS 3 / SATA 3 (SAS 12G/s, SATA still 6G/s), BUT 4 of the slots are hybrid slots and can handle NVMe drives! No expander, it's a direct attach backplane. Actually affordable and my recommend option.

Note 2: Power Supplies.
Standard redundant / hot swappable Supermicro PSUs (they also have other formats for WIO chassis etc.) have Goldfinger output as Supermicro calls it.
The Goldfinger output has a certain size, starting at 19 pairs, 23 pairs, 25 pairs and 27 pairs (although 25 pairs is very rare afaik).
The power distribution backplanes in turn have a connector that also has a certain size. Power distribution backplanes for smaller / cheaper servers have smaller inputs.

As you can imagine: Power Supplies with a bigger output don't fit into a power distribution backplane with a smaller input (i.e. 23-pair PSU won't fit into a 19-pair PDB), although I've heard that PDBs can be modded to allow any input connector size by cutting open the sides of the input connectors (have not tried that myself yet).

However PSUs with smaller output fit into PDBs with a bigger input (i.e. a 19-pair PSU WILL fit into a 23-pair PDB).

Why is this relevant?
Supermicro 826 comes in two revisions. Older revs have the PDB-PT825-8824 which has 19-pairs input, newer revs have the PDB-PT826-8824 which has a 23-pairs input.

Note 3: Chassis rev in general
Supermicro Chassis exist in different revisions.

I know there are at least two 826 revs:
Newer 826 revs: PDB-PT826-8824 (23-pairs input) and the possibility to for an additional 2x 2,5" hot swap tray on the rear
Older 826 revs: PDB-PT825-8824 (19-pairs input), no mounting point for the 2x 2,5" hot swap tray on the rear.

Older 826s can be upgraded to newer 826 by swapping the rear window (available as a replacement part through various distributors) and swapping the power distribution backplane.

Some Supermicro chassis had issues with a missing standoff in older revision (e.g. 825), although that is only relevant for E-ATX boards. However, as far as I know, 826s are NOT affected and always have the standoff position for E-ATX boards available (near the I/O shield)
 

spikeb

New Member
Apr 28, 2021
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Wow, I hit the jackpot, thank you *SO* much for your such a comprehensive answer. I've been buying SAS backplanes enabled chassis (mostly in 24 disks and 36 disk chassis) for years, and still didn't have the information you posted.

I do need some redundant caching, so pondering 2 x M.2 vs NVMe on U.2. For this case the hot-swap isn't particularly important for the cache drives. Unfortunately I am hoping to expand to 12 spinning disks, so if I want NVMe on U.2 I'd need 16 bays instead of 12.

In particular I was puzzled by the mentions of a dual port SAS only handling 8 drives, but you cleared that up with the "BPN-SAS3-826EL1 -> SAS 3 / SATA 3 (SAS 12G/s, SATA still 6G/s), has an expander on board -> No additional HBA needed, standard 2 port HBA is enough ...Note that this provides 4 times the total bandwidth compared with the SAS2 version (2 inputs instead of one and SAS3 instead of SAS2) ". That math works out, which helps verify it's working the way I expect.

That looks perfect for my use, granted it's overkill (4 x 12gbit is plenty for 12 drives with a max headrate of 242MB/sec or so) in fact the single SAS links has about twice the bandwidth of the drives, which I find about the ratio that ensures it won't be a bottleneck. Hard to complain about a second SAS for bandwidth overkill and redundancy.

A similar chassis I found once I checked out the 826 is the: 2014CS-TR | 2U | A+ Servers | Products | Super Micro Computer, Inc.

It's nice, integrated, no worries about compatible PS cables or headers, but does seem to be missing the 1 or 2 ports SAS -> backplane/expander. I'd rather not have per drive data cables for airflow, simplicity, and redundancy reasons.

Thanks again for the awesome reply.
 
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