Solved! Can I Plug A SAS Spinning Disk Into A MiniSAS/U.2 Port?

Jan 13, 2022
52
1
11
Hello,

My company plans on building an Enterprise-level server (running 24/7) and for spinning disks, I wanted to go with SAS hard drives rather than SATA hard drives, as I've heard SAS drives tend to be a bit more reliable (and possibly a little bit faster).

I plan on using the following Threadripper Pro motherboard: ASUS Pro WS WRX80E-Sage SE WIFI - https://www.asus.com/Motherboards-Components/Motherboards/Workstation/Pro-WS-WRX80E-SAGE-SE-WIFI/

...with the following two ports:

2x SFF-8643/U.2/Mini-SAS (PCIe 4.0 x4)

...and was wondering if I could plug in a SAS drive like the following (with the correct cable):

https://geizhals.eu/western-digital-ultrastar-dc-hc550-18tb-wuh721818al5201-0f38352-a2322036.html?hloc=at&hloc=de&hloc=eu&hloc=pl&hloc=uk

If it is possible to use a SAS hard drive, do I also need to have a SAS controller (as I'm not sure the motherboard has one)?

Lastly, what cable would I use to connect the SAS hard drive to the U.2/minisas port?

Note: If it's not possible to utilize the U.2/minisas port on the motherboard for the SAS drives, is there much of a difference in reliability with HGST's SAS drive:

https://geizhals.eu/western-digital-ultrastar-dc-hc550-18tb-wuh721818al5201-0f38352-a2322036.html?hloc=at&hloc=de&hloc=eu&hloc=pl&hloc=uk

...and SATA drive:

https://geizhals.eu/western-digital-ultrastar-dc-hc550-18tb-wuh721818ale6l5-0f38460-a2322028.html?hloc=at&hloc=de&hloc=eu&hloc=pl&hloc=uk

Thank you,
Nelson
 

thecoolnessrune

Diamond Member
Jun 8, 2005
9,627
527
126
The U.2 ports on that motherboard connect to the WRX80 chipset. Those ports can act as 4x PCIe lanes to connect to a 4x lane NVMe drive, OR they can work as 4 SATA III ports, each connected to a PCIe 1x lane internally to the WRX80 SATA Controller. They cannot work as SAS.

The datasheet for the DC550 is on Western Digital's Website. Both SAS and SATA disks have the same MTBF. https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/data-center-drives/ultrastar-dc-hc500-series/data-sheet-ultrastar-dc-hc550.pdf

SAS's benefits are stronger signaling voltages for longer runs through noisy storage Backplanes, as well as Duplex signaling vs. Simplex for SATA. SAS can also allow dual-homing via Dual Port connectors to two separate controllers for high availability, but that's not applicable to this use case of using on-motherboard connectors.

Today in the Enterprise Market, SATA and SAS are often the same, and there's been a resurgence of SATA in the Enterprise Market around Big Data and Cloud Storage because of a number of factors.

1. The use cases like Cloud Storage and Big Data have built-in resiliency. It often doesn't matter if a whole Controller fails because other drives in the Datacenter can rebuild the data.
2. Cloud Storage and Big Data are using big spinning disks for capacity, and aside from Seagate's new Dual Actuator Drives, HDD's can only read or write at any one moment, so the fact that SATA is limited to Simplex operation is no big deal.
3. Controllers are a lot better today than in the past when it comes to noise handling, so the lower voltage signaling of SATA is not usually an issue in a properly engineered system.
4. Implementing SATA is cheaper than implementing a dual port SAS.
5. Implementing semi-proprietary Sector Sizes in SAS, like 528 byte, or 4160 byte, used for on-disk sector checksumming by data storage operating systems like NetApp ONTAP and many others, isn't needed for these use cases because the Cloud / Big Data storage systems already perform data level scrubbing and resiliency checks regularly.

In the case of the DC550, regardless of whether you buy SATA or SAS, you're getting the same internals, just with a cheaper interface.

Note that as we've discussed in your other threads, you should check and double check that your Operating System will be compatible with the WRX80 chipset SATA Controller. Consumer and consistently updated OS's will have no issues, but Enterprise OS's are another matter.
 

damian101

Senior member
Aug 11, 2020
291
107
76
With the proper cable you can directly connect up to 4 SAS drives to a miniSAS port. However, not a U.2 port, that does not support SAS, even though the physical connector is identical. U.3 will support both PCIe and SAS.
 

thecoolnessrune

Diamond Member
Jun 8, 2005
9,627
527
126
The U.2 ports on that motherboard connect to the WRX80 chipset. Those ports can act as 4x PCIe lanes to connect to a 4x lane NVMe drive, OR they can work as 4 SATA III ports, each connected to a PCIe 1x lane internally to the WRX80 SATA Controller. They cannot work as SAS.

The datasheet for the DC550 is on Western Digital's Website. Both SAS and SATA disks have the same MTBF. https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/data-center-drives/ultrastar-dc-hc500-series/data-sheet-ultrastar-dc-hc550.pdf

SAS's benefits are stronger signaling voltages for longer runs through noisy storage Backplanes, as well as Duplex signaling vs. Simplex for SATA. SAS can also allow dual-homing via Dual Port connectors to two separate controllers for high availability, but that's not applicable to this use case of using on-motherboard connectors.

Today in the Enterprise Market, SATA and SAS are often the same, and there's been a resurgence of SATA in the Enterprise Market around Big Data and Cloud Storage because of a number of factors.

1. The use cases like Cloud Storage and Big Data have built-in resiliency. It often doesn't matter if a whole Controller fails because other drives in the Datacenter can rebuild the data.
2. Cloud Storage and Big Data are using big spinning disks for capacity, and aside from Seagate's new Dual Actuator Drives, HDD's can only read or write at any one moment, so the fact that SATA is limited to Simplex operation is no big deal.
3. Controllers are a lot better today than in the past when it comes to noise handling, so the lower voltage signaling of SATA is not usually an issue in a properly engineered system.
4. Implementing SATA is cheaper than implementing a dual port SAS.
5. Implementing semi-proprietary Sector Sizes in SAS, like 528 byte, or 4160 byte, used for on-disk sector checksumming by data storage operating systems like NetApp ONTAP and many others, isn't needed for these use cases because the Cloud / Big Data storage systems already perform data level scrubbing and resiliency checks regularly.

In the case of the DC550, regardless of whether you buy SATA or SAS, you're getting the same internals, just with a cheaper interface.

Note that as we've discussed in your other threads, you should check and double check that your Operating System will be compatible with the WRX80 chipset SATA Controller. Consumer and consistently updated OS's will have no issues, but Enterprise OS's are another matter.
 

Tech Junky

Senior member
Jan 27, 2022
848
272
96
Drives / capacity / density / speed

Depends on what the server will be doing. If it's high transactional data then going to a higher bandwidth disk setup makes more sense than bulk storage for hoarding data.

U.2/3 disks offer higher speeds / lower capacity in a 2.5" format
SAS can offer double the speed of SATA on the controller 12gb/s vs 6gb/s

However SATA can meet / beat the speed/capacity issues you run into above. If you structure the drives correctly using Raid you can hit those higher speeds at a lower cost per TB. If you want a huge pool of storage then you should be looking at supplementing the server with a SAN box that hangs off the server. Using a DAC cable you can have blistering speeds between the devices and not be restricted by the MOBO you're planning on using. If you want to go bigger and use multi-CPU setup for performance you would be able to concentrate your efforts on processing and just link them to the storage w/o worrying about the ports on the MOBO and add a couple of PCI cards to handle storage transport.
 

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