Title Photo by Magnus Engø on Unsplash

Supermicro SC846 is a great chassis for homelab users, which offering 24 3.5inch hard drive bay with varieties of backplanes. Most users buy second-hand chassis and want to change backplane because it doesn’t fit their needs. I list all backplanes for SC846 until April 2020 and also my recommendations for the different use cases.

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Price, availability and recommendations based on information from the first season of 2020.

Supermicro SC846 Backplane List

NameDrive PortHBA PortSAS TypeExpanders CableRequired HBAComment
BPN-SAS-846TQ24 SAS/SATA24 SAS/SATASAS 1
SAS 2
SAS 3*
0SAS 1 & 2:
SFF-8087 to SAS/SATA x 6

SAS 3 *:
SFF-8643 to SAS/SATA x 6
SAS 1 & 2:
SFF-8087 x 6

SAS 3 *:
SFF-8643 x 6
No expander,
Physical connection to all ports.

* No official SAS 3 support.

I own one of this backplane.
BPN-SAS-846A24 SAS/SATA6 SFF-8087SAS 1
SAS 2
SAS 3*
0SAS 1 & 2:
SFF-8087 to SFF-8087 x 6

SAS 3 *:
SFF-8643 to SFF-8087 x 6
SAS 1 & 2:
SFF-8087 x 6

SAS 3 *:
SFF-8643 x 6
No expander,
Physical connection to all ports.

* No official SAS 3 support.

I own one of this backplane.
BPN-SAS-846EL124 SAS/SATA3 SFF-8087SAS 1 1SAS 1:
SFF-8087 to SFF-8087 x 1
SAS 1:
SFF-8087 x1
SAS1 support only.
Slow, Do not buy.
BPN-SAS-846EL224 SAS/SATA6 SFF-8087SAS 1 2SAS 1:
SFF-8087 to SFF-8087 x 2
with dual HBA
SAS 1:
SFF-8087 x2
SAS1 support only.
Work with 2 HBA.
Slow, Do not buy.
BPN-SAS2-846EL124 SAS/SATA3 SFF-8087SAS 21SAS 2:
SFF-8087 to SFF-8087 x 1
SAS 2:
SFF-8087 x1
I own one of this backplane.
BPN-SAS-846EL224 SAS/SATA6 SFF-8087SAS 2 2SAS 2:
SFF-8087 to SFF-8087 x 2
with dual HBA
SAS 2:
SFF-8087 x2
Work with 2 HBA.
BPN-SAS3-846EL124 SAS/SATA4 SFF-8643SAS 31SAS 3:
SFF-8643 to SFF-8643 x 1
SAS 3:
SFF-8643 x1
BPN-SAS3-846EL224 SAS/SATA8 SFF-8643SAS 32SAS 3:
SFF-8643 to SFF-8643 x 2
with dual HBA
SAS 3:
SFF-8643 x2
Work with 2 HBA.
BPN-SAS3-846EL1-N824 SAS/SATA
8 Port shared with NVME
SFF-8643
8 SFF-8611 or
8 SFF-8643
SAS 31SAS 3:
SFF-8643 to SFF-8643 x 1
SFF-8611 to SFF-8611 x 8 or
SFF-8611 to 8643 x 8
SAS 3:
SFF-8643 x1
SFF-8611 x8 or
SFF-8643 x 8
Work with NVME.

Pass-Through Backplanes

BPN-SAS-846TQ
Simple direct pass-through backplanes with 24 SAS/SATA connector.

It supports SAS-1, SAS-2 and also conforms work on SAS-3 with SAS-3 with full 12Gb/s speed although it’s not officially supported by Supermicro. This backplane does not have expander chip, each SAS port need connect directly to HBA or RAID controller, or an extra SAS expander.

To connect all drive, you need:
– 3 x 8 port HBA/RAID Controller or
– 1 x 24+ port expander with 1 x HBA/RAID Controller

You need SAS to 4 SATA split cable to connect all drive:
– 6 x SFF-8087 to SAS/STAT cable for SAS-1 and SAS-2 HBA/RAID Controller or
– 6 x SFF-8643 to SAS/STAT cable for SAS-3 HBA/RAID Controller

BPN-SAS-846TQ is one common backplane usually comes with low priced SC846 chassis, I bought mine also come with the chassis. It is cheap and works with SAS-3. However, it requires massive cabling to each of the 24 SATA port, if you need LED status from your HBA / Controller, you also need a Sideband (SGPIO) cable for each 4 SATA group. Total 30 signal cable is a cable management nightmare and may cause issues with airflow. The backplane also requires more HBA / Controller or using an extra expander.

If you need pass-through backplanes, BPN-SAS-846A can be a better option with only 6 single cable required.

BPN-SAS-846A
Simple direct pass-through backplanes with 6 SFF-8087 connector.

Similer to BPN-SAS-846TQ, BPN-SAS-846A also supports SAS-1, SAS-2 and also conforms work on SAS-3 with SAS-3 with full 12Gb/s speed although it’s not officially supported by Supermicro. This backplane does not have expander chip, each SAS port need connect directly to HBA or RAID controller, or an extra SAS expander.

To connect all drive, you need:
– 3 x 8 port HBA/RAID Controller or
– 1 x 24+ port expander with 1 x HBA/RAID Controller

You need SAS to SAS cable to connect all drive:
– 6 x SFF-8087 to SFF-8087 cable for SAS-1 and SAS-2 HBA/RAID Controller or
– 6 x SFF-8643 to SFF-8087 cable for SAS-3 HBA/RAID Controller

Channel for SFF-8087 Connector, from left to right of the picture above:
– Left #1 top: Channel 20-23
– Left #2 middle: Channel 16-19
– Middle: Channel 12-15
– Right #1 top: Channel 8-11
– Right #2 middle: Channel 4-7
– Right #3 lower: Channel 0-3

BPN-SAS-846A is another common backplane you can buy with SC846 chassis or buy it separately. It is cheap and works with SAS-3, I have my Seagate ST8000NM0065 SAS-3 Drive connected and show negotiate speed 12Gb/s on LSI 9361 controller. It still requires 6 sick SAS cable, but it much better than 24 or 30 cables on TQ board.

This backplane is a very good option for people not using a hardware RAID controller, especially zfs, FreeNAS, Unraid and OpenMediaVault user. You can have link speed to every drive with 3 cheap standard 8-port HBA.

People using RAID with hardware controller should consider EL backplane. You may need more than one expensive controller or using an expander, unless you need SAS line speed on every port, or need SAS-3 connection but not able to get SAS-3 EL backplane which is also expensive and hard to buy.

SAS-1 Backplanes

BPN-SAS-846EL1
Backplanes with one expander and only work with SAS-1

BPN-SAS-846EL1 is old obsolete backplane support only 3Gb/s connection speed which is too slow for most SSD. It also has issues with hard drive large than 2TB.

To connect all drive, you need:
– 1 x 8 port HBA/RAID Controller

You only need 1 SAS to SAS cable to connect all drive:
– 1 x SFF-8087 to SFF-8087 cable for SAS-1 and SAS-2 HBA/RAID Controller or
– 1 x SFF-8643 to SFF-8087 cable for SAS-3 HBA/RAID Controller

You can connect all three with SFF-8087 to an HBA or controller with 12 lane support. With typical 8 lane HBA and controller and two SAS cable from the backplane, the maximum speed is 24Gb/s.

This backplane does not have multipath support. You can not connect to more than one HBA or controller.

BPN-SAS-846EL2
Backplanes has two expanders but only work with SAS-1

BPN-SAS-846EL2 is old obsolete backplane support only 3Gb/s connection speed which is too slow for most SSD. It also has issues with hard drive large than 2TB. Compare to BPN-SAS-846EL1, it has an additional expander chip for multipath failover support.

To connect all drive, you need:
– 1 x 8 port HBA/RAID Controller

You only need 1 SAS to SAS cable to connect all drive:
– 1 x SFF-8087 to SFF-8087 cable for SAS-1 and SAS-2 HBA/RAID Controller or
– 1 x SFF-8643 to SFF-8087 cable for SAS-3 HBA/RAID Controller

You can connect all three with SFF-8087 to an HBA or controller with 12 lane support. With typical 8 lane HBA and controller and two SAS cable from the backplane, the maximum speed is 24Gb/s.

This backplane supports multipath with failover only in an active/standby mode, you will not get extra bandwidth between the backplane and system.
SAS drive and additional HBA or controller are required for multipath. SATA drive does not support this feature.

SAS-2 Backplanes

BPN-SAS2-846EL1
Backplanes with one expander and support SAS-2.

BPN-SAS2-846EL1 is a popular backplane for Homelab builders. With SAS-2 6Gb/s support, you will get reasonable speed from typical SATA SSD. With typical 8 lanes HBA or controller, 48Gb/s board to controller bandwidth is enough for 24 hard drive at 200MB/s speed.

To connect all drive, you need:
– 1 x 8 port HBA/RAID Controller

You only need 1 SAS to SAS cable to connect all drive:
– 1 x SFF-8087 to SFF-8087 cable for SAS-2 HBA/RAID Controller or
– 1 x SFF-8643 to SFF-8087 cable for SAS-3 HBA/RAID Controller

You can connect all three with SFF-8087 to an HBA or controller with 12 lane support. With typical 8 lane HBA and controller and two SAS cable from the backplane, the maximum speed is 48Gb/s.

This backplane does not have multipath support. You can not connect to more than one HBA or controller.

BPN-SAS2-846EL2
Backplanes has two expanders with SAS-2 support.

BPN-SAS2-846EL2 is a two expander version backplane with SAS-2 6Gb/s support, you will get reasonable speed from typical SATA SSD. With typical 8 lanes HBA or controller, 48Gb/s board to controller bandwidth is enough for 24 hard drive at 200MB/s speed. Compare to BPN-SAS2-846EL1, it has an additional expander chip for multipath failover support.

To connect all drive, you need:
– 1 x 8 port HBA/RAID Controller

You only need 1 SAS to SAS cable to connect all drive:
– 1 x SFF-8087 to SFF-8087 cable for SAS-2 HBA/RAID Controller or
– 1 x SFF-8643 to SFF-8087 cable for SAS-3 HBA/RAID Controller

You can connect all three with SFF-8087 to an HBA or controller with 12 lane support. With typical 8 lanes HBA and controller and two SAS cable from the backplane, the maximum speed is 48Gb/s.

This backplane supports multipath with failover only in an active/standby mode, you will not get extra bandwidth between the backplane and system.
SAS drive and additional HBA or controller are required for multipath. SATA drive does not support this feature.

SAS-3 Backplanes

BPN-SAS3-846EL1
Backplanes with one expander and support SAS-3

BPN-SAS3-846EL1 is a newer SAS-3 12Gb/s backplane. You will get pretty good speed from typical SATA SSD at 1GB/s. With single 4 lanes SAS cable, 48Gb/s board to controller bandwidth is enough for 24 hard drive at 200MB/s speed. With typical 8 lan 2 SAS cable configuration, 96Gb/s is enough for SSD cached solution.

To connect all drive, you need:
– 1 x 8 port HBA/RAID Controller

You only need 1 SAS to SAS cable to connect all drive, but typical using 2 cable:
– 2 x SFF-8643 to SFF-8087 cable for SAS-2 HBA/RAID Controller or
– 2 x SFF-8643 to SFF-8643 cable for SAS-3 HBA/RAID Controller

You can connect all four with SFF-8087 to an HBA or controller with 16 lane support. With typical 8 lane HBA and controller and two SAS cable from the backplane, the maximum speed is 96Gb/s.

This backplane does not have multipath support. You can not connect to more than one HBA or controller.

BPN-SAS3-846EL2
Backplanes has two expanders with SAS-3 support.

BPN-SAS3-846EL2 is an expensive two expander version backplane with SAS-3 12Gb/s support, You will get pretty good speed from typical SATA SSD at 1GB/s. With single 4 lane SAS cable, 48Gb/s board to controller bandwidth is enough for 24 hard drive at 200MB/s speed. With typical 8 lanes 2 SAS cable configuration, 96Gb/s is enough for SSD cached solution. Compare to BPN-SAS3-846EL1, it has an additional expander chip for multipath failover support.

To connect all drive, you need:
– 1 x 8 port HBA/RAID Controller

You only need 1 SAS to SAS cable to connect all drive, but typical using 2 cable:
– 2 x SFF-8643 to SFF-8087 cable for SAS-2 HBA/RAID Controller or
– 2 x SFF-8643 to SFF-8643 cable for SAS-3 HBA/RAID Controller

You can connect all four with SFF-8087 to an HBA or controller with 16 lane support. With typical 8 lane HBA and controller and two SAS cable from the backplane, the maximum speed is 96Gb/s.

This backplane supports multipath with failover only in an active/standby mode, you will not get extra bandwidth between the backplane and system.
SAS drive and additional HBA or controller are required for multipath. SATA drive does not support this feature.

SAS-3 and NVME Backplane

BPN-SAS3-846EL1-N8
Backplanes with SAS-3 and NVME support.

BPN-SAS3-846EL1-N8 is the only SAS-3 12Gb/s backplane with NVME support. It has the same SAS performance as BPN-SAS3-846EL1. With single 4 lane SAS cable, 48Gb/s board to controller bandwidth is enough for 24 hard drive at 200MB/s speed. With typical 8 lanes 2 SAS cable configuration, 96Gb/s is enough for SSD cached solution.

SAS port 16-23 also support 2.5 inch NVME, you can connect 8 SFF-8611 to 8 SFF-8611 cable with PCIe adapter.

To connect all drive, you need:
– 1 x 8 port HBA/RAID Controller
– 2 x 4 Port NVMe adapter

You only need 1 SAS to SAS cable to connect all drive, but typical using 2 cable:
– 2 x SFF-8643 to SFF-8087 cable for SAS-2 HBA/RAID Controller or
– 2 x SFF-8643 to SFF-8643 cable for SAS-3 HBA/RAID Controller

You can connect all four with SFF-8087 to an HBA or controller with 16 lane support. With typical 8 lane HBA and controller and two SAS cable from the backplane, the maximum speed is 96Gb/s.

This backplane supports multipath with failover only in an active/standby mode, you will not get extra bandwidth between the backplane and system.
SAS drive and additional HBA or controller are required for multipath. SATA drive does not support this feature.

You need 8 cables to connect all NVME drive:
– 8 x SFF-8611 to SFF-8611 cable for SFF-8611 PCIe adapter
– 8 x SFF-8643 to SFF-8611 cable for SFF-8643 PCIe adapter
Each port support 2.5 inch NVME with 4x PCIe, with typical PCIe 3.0, each port can provide 32Gb/s bandwidth.

LSI 9400-series do not work with this backplane, and there are no hardware RAID with NVME cached solution.

Availability

  • Extreme Rare: BPN-SAS3-846EL1-N8. You can only get this board with selected brand new chassis or contact Supermicro support directly, even some authorised sellers don’t have pants on their hands.
  • Rare: All EL2 board with 2 chips, BPN-SAS-846EL2, BPN-SAS2-846EL2 and BPN-SAS3-846EL2
  • Not Common: BPN-SAS3-846EL1 because it is a current-generation backplane used in datacenter, many are brand new or high priced. The SAS-1 backplane, BPN-SAS-846EL1 and BPN-SAS-846EL2, also less available because they are obsolete.
  • Common: BPN-SAS-846TQ, BPN-SAS-846A are most common backplane with usually very low price. BPN-SAS2-846EL1 are also common. Those three boards are also popular for Homelab builders.

Availability of the backplanes is based on eBay US and Amazon US. As I am living in China I also search on Taobao (as AliExpress for outside of China). Order from an authorised retailer or order from Supermicro are not count as available, because Supermicro does not sell backplane on their online store, and most of the homelab builder do not access to an authorised retailer as some parts may require a service contract of the chassis, and brand new parts are usually overpriced compare to pre-owned.

Price

  • Extremely Expensive (USD 1000+): BPN-SAS3-846EL1-N8. You can only get from Supermicro and expect a high price. BPN-SAS3-846EL2 is also extremely expensive because it is a current-generation board and low availability.
  • Expensive (USD 500+): BPN-SAS-846EL2 and BPN-SAS2-846EL2 because of low availability.
  • Slightly Expensive (USD 300-400): BPN-SAS3-846EL1. It is a current-generation board and higher performance than BPN-SAS2-846EL1.
  • Affordable (USD 100-300): BPN-SAS2-846EL1. Most common backplane with expander. BPN-SAS-846EL2 sometimes priced as less than USD 200, but it’s obsolete.
  • Cheap (Less than USD 100): BPN-SAS-846TQ, BPN-SAS-846A are most common backplane with usually very low price. They work with SAS-3 and extra expander. BPN-SAS-846EL1 is also cheap because of obsolete.

Price of the backplanes are also based on eBay US and Amazon US. As I am living in China I search on Taobao (as AliExpress for outside of China). Most of the price is based on pre-own item, brand new backplanes are usually much expensive, but they do not perform differently to pre-own ones.

TL; DR

Buy

For people need line speed, buy BPN-SAS-846A because it conformed work with SAS-1, SAS-2 as well as SAS-3, and it doesn’t have bottleneck due to no expansion chip. Alternatively, BPN-SAS-846TQ can be a backup option, but cable management can be an issue.

For power users, buy BPN-SAS3-846EL1 if available, it offers 8 12Gb/s SAS channel to common 8 port HBA or controller. BPN-SAS-846A with an extra SAS-3 expander can do the same thing with more flexibility and slightly cheaper costs (around USD 100-150 less), but you need a good expander and total of 8 SAS cable to compare to 2 SAS cable with the BPN-SAS3-846EL1.

For most users, if you can find BPN-SAS3-846EL1 and it’s affordable for you, but it. It provides 48Gb/s speed between backplane with single SAS cable and 96Gb/s with two SAS cable to HBA or controller, which is sufficient for few modern 12Gb/s SSD drives. The alternative option is BPN-SAS2-846EL1 without SAS-3 support and lower bandwidth.

Not to buy

Do not buy SAS-1 backplane with an explainer: BPN-SAS-846EL1 and BPN-SAS-846EL2. They are slow to modern drive and have issues with drive large than 2TB. They are obsolete.
Note, pass-though backplane also name as BPN-SAS-846TQ and 846A, they work with SAS-1, SAS-2 and even SAS-3, they are not obsolete.

Do not buy EL2 backplane with an 2 explainer chip, BPN-SAS-846EL2, BPN-SAS2-846EL2 and BPN-SAS3-846EL2. They are expensive and or hard to find. The dual controller configuration is not common in a Homelab build, they do little good but cost a lot. Those backplane are not worse the price you pay.

BPN-SAS3-846EL1-N8: do not buy unless you know what you are doing. It is too expensive, and you can not even find a place sells it. For RAID user LSI RAID controller does not support NVME catching. And LSI 9400-series do not work with this backplane.
If you are software raid user, mount your 2.5-inch U2 drive to internal bay, or using a different type of NVME drive such as AIO card or mount your NVME stick to an adapter.

Backplanes User Manual

3 comments

  1. 难得看到和我一样喜欢仔细研究的diyer。我在找BPN-SAS3-846EL1-N8,zfs配合它真是完美。前提是可以用合理的价格找到。

    1. SAS3的背板不仅贵,而且真的好难找。不过说实话,对于机械硬盘,SAS2和SAS3的速度几乎无差别。而对于SSD,用zfs的话而且是4U的846,个人感觉还是用PCIe的SSD更方便。双路的主板一般不缺PCIe插槽,而且用U2盘,不仅盘架要2.5转3.5,而且还要OCuLink SFF-8611 (x4) to SFF-8639 U.2转到NVME的AOC上,例如AOC-SLG3-2E4。

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