What is the difference between a sas controller and a sas raid controller? Are they the same thing, just named differently, or is the SAS Controller purely a connection point with no RAID capabilities and the SAS Raid Controller is something that can be configured (somehow?)
RAID – Difference Between SAS Controller and SAS RAID Controller
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As long as your controller supports it, there's no reason why you can't set up two logical drives (1 SAS, 1 SATA). If it doesn't support it for some reason, buy a cheap SATA controller and throw it into the machine.
A few items to help clarify SAS technology...
- SATA drives can connect to SAS ports.
- SAS drives cannot connect to SATA ports.
- Server-class hardware typically uses an embedded RAID controller or a separate RAID controller PCIe device.
- Most RAID controllers and SAS HBAs will use SAS connections (multilane or 4-lane SAS ports).
- Internally, these systems will use one of the internal SAS transports (SFF-8087 or SFF-8484) for cabling.
- 4-lane SAS cables carry FOUR SAS links over the same cable.
- Enterprise servers will typically have a SAS backplane for hot-swap hard drives. These backplanes can accommodate SAS and SATA disks. The backplanes also provide power to the drives. It doesn't make sense to run SATA cables to hot-swappable hard drives. Instead, the internal SAS cables will link the controller and the backplane.
- You can mix and match SATA and SAS on the same backplane, but because the protocols are different, bad things. can happen.
Internal SAS 4-lane cabling to a backplane
Internal SAS breakout cabling to a backplane
Best Answer
A SAS controller (HBA, Host Bus Adapter) on its own has no RAID ability. It just presents however many disks are plugged in to the underlying operating system, and it's the OS's job to figure out what to do with them.
A RAID controller has a processor (and it should also have some RAM) embedded on the card itself. That RAM acts as a cache, and the processor does RAID functionality. The number of disks that the underlying OS sees depends on how you configure your RAID volumes.
A SAS HBA typically also supports non-disk based devices, such as a tape drive. RAID controllers typically do not.
A SAS or RAID controller is typically backwards compatible with SATA disks, but whether or not you can mix SATA and SAS on the same card depends on the card.
If you are using a modern software storage solution like ZFS or Windows Storage Spaces then a SAS HBA (non-raid) may be all you need, at a much lower cost.
Note that you may be limited by the speed of the PCIe lanes or the RAID controller in both these cases. A mid-tier RAID card usually caps out at around 700MB/sec, whereas just a SAS controller can probably saturate an 8x PCIe link (~7000MB/sec if the disks on the other end can keep up).