You can often find SAS (Serial Attached SCSI) drives cheap online, thanks to their use in enterprise environments, where drives need to be upgraded periodically for better reliability. However, one downside to buying them is their lack of support in consumer hardware.
It’s easy to mistake these drives for the more common SATA (Serial ATA) drives. They share the same form factor and have a nearly identical connector, save for four additional pins on a SAS connector, leading to the compatibility of SATA drives with the SAS interface.
Unfortunately, the reverse is not valid, which means a SAS drive cannot connect to the existing SATA ports on your motherboard. So, your only option is through a universal interface like PCI Express or PCIe found on most modern motherboards.
PCIe is one of the fastest ways you can connect peripherals to your PC. It’s commonly used for connecting graphics cards and high-speed NVMe storage devices that need multiple lanes of high-bandwidth connectivity.
HBAs and RAID controllers
The most common way of connecting drives via PCIe is through an HBA. RAID controllers are similar to HBAs but feature support for hardware-accelerated RAID, which most general consumer systems do not need. Software RAID performs better and is easier to use.
Most OEMs like Dell, HP, and IBM often use RAID controllers that are just HBAs flashed with custom firmware. If you get hold of such a RAID controller, we recommend you flash it to IT mode. RAID controllers tend to work with only specific models of hard disks belonging to the same OEM and have restrictions on the maximum number of drives that can be attached.
Keep in mind that support for IT mode flashing depends on the controller, so it’s best to get one that’s already been flashed. If you bought an unflashed controller, you could find guides online by searching your RAID controller’s model no. Some controllers don’t support this, so make sure to consult this list before purchasing one.
SAS Expanders and DAS
For additional expansion, SAS expanders help split a single connection from your HBA into multiple ports for connecting more HDDs. A SAS expander like Intel’s RES2SV240NC lets you add up to 20 additional drives for adding more drives. You will also need suitable cables that connect the drives to the HBA or SAS expanders.
Direct Attached Storage or DAS works on a similar principle but is used for external storage of drives if your current PC is limited in space and dramatically reduces clutter by using much fewer cables. Drives are placed into caddies and slide into their respective slots without the need of wiring up each drive individually.
Choosing the right hardware
Most hard disks have speeds of 6 or 12 Gbps, which can let you theoretically connect up to 42 of them to a full-sized PCIe Gen 4 slot on your motherboard. For comparison, a modern GPU like Nvidia’s flagship 3090 supports the same number of lanes, while a high-speed Gen 4 NVMe SSD takes four.
This implies enough lanes on current generation motherboards to connect multiple HDDs directly to your PC. However, if you want each HDD to have a bandwidth of at least 6 Gbps, costs are going to pile up.
For reference, a new Gen 4 9500-16i HBA will set you back $833 at current market prices. Adding a suitable 12Gbps SAS expander to the mix will add another $355 to your budget. If you need the highest bandwidth per drive and can afford the costs, we recommend this setup.
Older generation used HBAs like this LSI 9211-8i are a cheaper solution suitable for home or small business use. You will lose out on a per-drive bandwidth, especially when adding multiple HDDs due to the slower PCIe 2.0 interface., but considering most use their drives in some form of RAID, this is an excellent solution for adding SAS drives to your PC.
Art of Server’s YouTube video compares the various models of HBAs available on the market and is worth a watch before investing in an HBA:
In conclusion, if you’re getting a good deal on used or refurbished SAS drives, then buying an HBA and a SAS Expander should help you connect these drives to your PC with ease.
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